Im gettin 11.9 mpg in 92 sonata 6 cylinder(3.0) I was told it could b my brain box. Would that be the engine control unit or the engine control module?

no, no, and no.... (yes is pure electronics theory but not in practice)
NO Car told told or year.
no VIN told (USA?>)
no engine told.size , gas ,diesel LPG, LNG, hydrogen (LOL)
here is the ageless generic answer, ready?

1. tires are not full of AIR, spec told on drivers door jamb
2. right foot too heavy. (or jack rabbit starts) Lemans style?
3. engine needs a tune up SPARK and filters.
4. engine sick, NOT PCM brain box, no. do engine tests.(skills)
5. bad spark, misfiring, spark plugs and cop boots,. HV sets.
6. bad fueling too rich. fuel pressure too high. FPR bad.
7. a load of bricks in the trunk? << sorry.
8. bad 02 sensors (oxygen) front ones only.
9. Not doing MPG the correct way . no 2 gas pumps trip off same spot. see?????? (caused huge errors in gas used) do not top off(forced at station nozzle)
10. to cure #9, do averages. or buy a MPG gauge.(instrument)
11. bad wheel bearings,
12. dragging brakes.
13. transmission fails to use ALL GEARS. (A/T BOX)
14. bad MAP sensor on engine, reads VAC too low.
15. engine compression low for sure on one cylinder, causing others to work too hard. and dragging it around. dead.
16. air filter bad? packed up?
17. check engine lamp on, scans fail?
18. this list is in no order of likely.

good luck and a great question. for sure $7 fuel, sure.
get a car with 1 liter engine like they do in Europe and 5speed manual box to save more fuel;. avoid cars with 10 speed bear boxes.
they love to fail and when do have $5000 extra cash ready with no need for that cash. new cars like that 10T1000 stink, << transmission name GM or the like.

not told what car or MPG Now.
so list is huge.

no problem told just the word problem
is the scan tool dead?
you are super confuse
this cars PCM has complex timing tables in the PCM that only it controls NOT YOU ever, welcome to modern cars?
The timing tables under all conditions are indexed by the PCM
using engine RPM ,engine load, and even knock sensors.\
same thing here from 1990 to now .
also that scan tool you have is telling huge lies to you;. useless it.
take and ASE class. to learn all this, do so now.
71degres advanced is a lie, bold face bunk.
20 or 30 is par, light cruise fast and is load based big time;

your scan tool is BUNK. (gutter fodder) KAPUT

These are the same bolt patterns, bolt pattern is 4 X 4.5 or also known as 4 X 114MM. Measure 2 lugholes across from each other and it should measure 4 1/2" US or 114MM. the center hubs may be smaller/larger. Check the center hub size before purchasing:
1997 Acura- CL 16 x 6 (5 straight spokes)
1998 Acura- CL 16 x 6 (5 dual straight spokes)
1998 Acura- CL 16 x 6 (7 straight spokes
1990-89 Acura- Legend 15 x 5.5
1996-95 Acura- TL 15 x 6 (5 straight spokes with groove)
1997-98 Acura- TL 15 x 6 (11 straight spokes)
1994-92 Acura- Vigor 15 x 6 (11 triangular slots)
1999-98 Chevrolet- Metro
1989-85 Chevrolet- Sprint
1991 Dodge- Colt Vista 13 x 5 (15 slots)
1993-92 Dodge- Colt Vista 14 x 5.5 (5 straight spokes)
1992-84 Eagle- Summit/Summit Wagon
1992-91 Eagle- Summit 13 x 5 (15 slots)
1993-88 Ford- Festiva 12 x 4 40mm offset
1993-91 Ford- Festiva 12 x 4.5 40mm offset (8 elongated triangle slots)
1997-89 Geo- Metro
1999-92 Honda- Prelude
1999-90 Honda- Accord (4 cylinder models)
1999-91 Hyundai- Elantra
1995-92 Hyundai- Elantra 14 x 6 (16 slots)
1995-92 Hyundai- Elantra 14 x 5.5 (7 curved spokes)
1998-96 Hyundai- Elantra 14 x 5.5 (5 straight spokes)
1999-90 Hyundai- Accent/Excel/Pony
1994-92 Hyundai- Excel 13 x 5
1991 Hyundai- Sonata 15 x 6 (18 rectangular slots)
1994-92 Hyundai- Sonata 15 x 6 (9 triangular slots)
1996-95 Hyundai- Sonata 15 x 6 (9 straight spokes)
1997-95 Hyundai- Sonata 15 x 6 (5 twisted spokes)
1998-97 Hyundai- Sonata 15 x 6 (5 straight single groove spokes)
1995-90 Hyundai- Scoupe
1992-91 Hyundai- Scoupe 14 x 5 (6 curved spokes)
1995-93 Hyundai- Scoupe 14 x 5 (5 curved spokes)
1998-97 Hyundai- Tiburon 15 x 6 (5 twisted spokes)
1998-97 Hyundai- Tiburon 15 x 6 (5 raised straight spokes)
1989-81 Mazda- 323/GLC
1985-84 Mazda- RX7 GSL-SE 14 x 5.5 40mm offset
1991-86 Mazda- RX7 14 x 5.5 40mm offset
1987-85 Mazda- 626/MX-6
1994-91 Mercury- Capri 14 x 5.5 45mm offset (16 holes)
1994-91 Mercury- Capri 15 x 6 45mm offset (3 curved spokes
1994-91 Mercury- Topaz 14 x 5.5 (16 holes)
1998-92 Mitsubishi- Expo/Expo LRV/Vista Wagon
1994-92 Mitsubishi- Expo 14 x 5.5 (5 straight spokes)
1999-84 Mitsubishi- Galant
1991 Mitsubishi- Galant 14 x 5.5 (18 slots)
1991 Mitsubishi- Galant 15 x 6 (8 straight spokes)
1991 Mitsubishi- Galant 15 x 6 (5 straight spokes)
1993-91 Mitsubishi- Galant 14 x 5.5 (15 slanted spokes)
1992 Mitsubishi- Galant 15 x 6 (5 straight spokes)
1993 Mitsubishi- Galant 15 x 6 (8 triangular and 8 rectangular slots)
1993-84 Mitsubishi- Mirage
1993-91 Mitsubishi- 2000GTX 14 x 5.5 (18 slots)
1991-80 Mitsubishi- Tredia
1999-93 Nissan- Altima
1995-82 Nissan- Stanza
1991-84 Nissan- Maxima
1990-78 Nissan- B310/Pulsar
1989-94 Nissan 240sx
1989-94 Nissan Silvia
1986-82 Nissan- Sentra
1993-84 Plymouth- Colt
1985-79 Plymouth- Arrow/Champ
1999-89 Suzuki- Swift
1991-80 Toyota- Cressida
1985-80 Toyota- Celica

you dont,you need the ecm from the newer motor,your old brain wont work

the fuel pressure regulator will not do it. you need to look at spark plugs ,wires ,air filter, fuel filter. tires pressure if tires are under pressure can cause bad gas mpg

Here is the code list for the 1990 OBD1 system on your Acura.
Code 0 and 11 Electronic Control Module (ECM)
Code1 Heated oxygen sensor A
Code 2 Oxygen content B
Code 3 and 5 Manifold Absolute Pressure
Code 4 Crank position sensor
Code 6 Engine coolant temperature
Code 7 Throttle position sensor
Code 8 Top dead center sensor
Code 9 No.1 cylinder position sensor
Code 10 Intake air temperature sensor
Code 12 Exhaust recirculation system
Code 13 Barometric pressure sensor
Code 14 Idle air control valve or bad ECM
Code 15 Ignition output signal
Code 16 Fuel Injector
Code 17 Vehicle speed sensor
Code 19 A/T lock-up control solenoid
Code 20 Electric load detector
Code 21 V-TEC control solenoid
Code 22 V-TEC pressure solenoid
Code 23 Knock sensor
Code 30 A/T FI signal A
Code 30 A/T FI signal B
Code 41 Heated oxygen sensor heater
Code 43 Fuel supply system
Code 45 Fuel supply metering
Code 48 Heated oxygen sensor
Code 61 Front heated oxygen sensor
Code 63 Rear heated oxygen sensor
Code 65 Rear heated oxygen sensor heater
Code 67 Catalytic converter system
Code 70 Automatic transaxle
Code 71 Misfire detected cylinder 1
Code 72 Misfire detected cylinder 2
Code 73 Misfire detected cylinder 3
Code 74 Misfire detected cylinder 4
Code 75 Misfire detected cylinder 5
Code 76 Misfire detected cylinder 6
Code 80 Exhaust recirculation system
Code 86 Coolant temperature
Code 92 Evaporative emission control system

Check Engine Light Codes and Meanings
Long blinks Short blinks Problem
1 1 Camshaft position sensor
1 2 Mass air flow sensor
1 3 Engine coolant temperature sensor
1 4 Speed sensor
1 11 EVAP control system (flow)
1 14 Fuel injection system right bank (too rich)
1 15 Fuel injection system right bank (too lean)
2 1 Ignition circuit
2 3 Closed throttle position switch
2 5 Idle speed control
2 9 Fuel Injection system left bank (too rich)
2 10 Fuel Injection system left bank (too lean)
3 1 ECU
3 2 Exhaust gas recirculation system flow problem
3 3 Front left O2 sensor
3 4 Knock sensor
3 5 Exhaust gas recirculation temperature sensor
3 6 EGRC-BPT valve
3 7 Closed loop control
3 8 Closed loop control
4 1 Air intake temperature sensor
4 2 Fuel tank temperature sensor
4 3 Throttle position sensor
4 7 Crankshaft position sensor
5 3 Front right O2 sensor
5 4 Automatic transmission control unit
6 3 Cylinder #6 misfire
6 4 Cylinder #5 misfire
6 5 Cylinder #4 misfire
6 6 Cylinder #3 misfire
6 7 Cylinder #2 misfire
6 8 Cylinder #1 misfire
7 1 Multiple cylinder misfire
7 2 Three way catalytic converter (right side)
7 3 Three way catalytic converter (left side)
7 4 Evaporative emission control system pressure sensor
7 5 Evaporative emission control system
7 7 Rear O2 sensor
8 1 Vacuum cut valve bypass valve
8 2 Crank position sensor
8 3 Absolute pressure sensor
8 4 Automatic transmission control unit
8 6 Evaporative emission canister purge control solenoid valve
8 7 Evaporative emission Canister purge control solenoid valve circuit
9 1 Front Right O2 sensor
9 3 Evaporative emission Canister vent control valve
9 5 Crankshaft position sensor
9 8 Engine coolant temperature sensor
10 1 Front left O2 sensor
10 3 Park and Neutral position switch
10 5 EGRC solenoid valve
10 8 Evaporative emission canister purge volume control valve
11 1 Inhibitor switch
11 2 Revolution sensor
11 3 Improper shifting to first gear (Automatic transmission)
11 4 Improper shifting to second gear (Automatic transmission)
11 5 Improper shifting to third gear (Automatic transmission)
11 6 Improper shifting to fourth gear (Automatic transmission)
11 7 Solenoid valve lock up function
12 1 Shift solenoid B (Automatic transmission)
12 3 Overrun clutch solenoid valve (Automatic transmission)
12 4 Torque converter clutch solenoid valve (Automatic transmission)
12 5 Line pressure solenoid valve (Automatic transmission)
12 6 Throttle position sensor (Automatic transmission)
12 7 Engine speed signal
12 8 Fluid temperature sensor
13 2 MAP/BARO Switch Solenoid Valve
13 5 Fuel pump control module
13 8 Cooling fan

Autozone.com says that for this vehicle the firing order is 1-2-3-4-5-6 and the set-up is 2/1 4/3 6/5 meaning that the #6 cylinder is far right on the back. It goes #1 #3 and #5 in the front and #2 #4 and #6 in the back.

check the fuel pressure regulator, the diaphrams rupture causing fuel to be sucked into engine / you could have an head gasket that needs to be replaced. do a compression test on all cylinders i think you will find atleast 1 cylinder real low.

For starters if your going to do 1 do all. The locations are from left to right when standing in front of the car. 1, 3, 5
2, 4, 6

wires are 3
6
2
4
5
1