What is causing intermittent lack of power?

I think I would check the fuel pressure and the maximum fuel pressure from the pump.
I would look to data if temp sensor , map, tps,
lack of power can be cause by many things
hope it helps

Replace the T.P.S. sensor." throttle position sensor"

throttle position sensor is bad

lots of odd things can happen in fuel injected cars sometimes the reverse of what you may expect. typically a malfunctioning O2 sensor can affect adjustments to TIMING thus for same accelerator position engine revs can rise/fall or become unstable just because O2 sensor is duff. if O2 bad poor acceleration/easy stall is definitely likely due to fluctuation in timing. can also cause pinking. best to check OBD codes if you can. some do not cause engine light to show and if intermittent, are cleared if you disconnect battery. check air filter and replace. if its diesel though you must suspect fuel pressure too.

suggestion.. lower exhaust pipe and drive car with exhaust disconnected, a possible clogged cat. converter.

The gas pedal is recalled on many fords and toyotas and is a well known problem, get the pedal replaced

This is a "Drive by wire" car on the throttle. There is no accelerator cable, it has an electrical sensor that tells the engine computer when you accelerate.

Sounds like the sensor is going bad. Take it to a shop and get it replaced.

The vehicle has a optional adjustable brake to increase driver comfort. The brake pedal position is changed in phase with the accelerator pedal. The system is adjusted by pressing the dash-mounted switch that powers the driver motor mounted on the accelerator pedal assembly. The two-way motor operates backward (away from the driver) or forward (toward the driver) to adjust the accelerator pedal directly and the brake pedal through the drive cable attached to the brake pedal assembly.
--------------------

• Adjustable brake pedal inoperative

• Switch.
• Circuit.
• Motor.
• Cable.
• Obstructions

------------------------------------
PINPOINT TEST D: ADJUSTABLE BRAKE PEDAL INOPERATIVE Test Step Result / Action to Take D1 CHECK MOTOR SOUND

• Allow two minutes for the thermal overload to reset.
• Operate the adjustable pedal control switch.
• Can the adjustable pedal motor be heard to operate?

Yes
GO to D2 .

No
GO to D7 . D2 CHECK MOTOR INSTALLATION

• Check adjustable pedal motor for correct installation.
• Is the motor installation OK?

Yes
GO to D3 .

No
CORRECT the motor installation. TEST the system for normal operation. D3 CHECK ADJUSTABLE ACCELERATOR PEDAL SYSTEM

• Disconnect the brake pedal-to-accelerator pedal cable.
  
• Operate the adjustable pedal control switch.
• Does the adjustable brake pedal operate now?

Yes
INSTALL a new adjustable brake pedal assembly. REFER to Section 206-06 . TEST the system for normal operation.

No
GO to D4 . D4 INSPECT FOR FOREIGN MATERIAL

• Inspect the adjustable accelerator pedal assembly for foreign material causing a binding condition.
• Was any foreign material found?

Yes
REMOVE the foreign material. RETEST for normal operation.

No
GO to D5 . D5 CHECK CABLE

• Detach the adjustable pedal motor cable.
• Inspect the ends of the brake pedal motor cable for wear or damage.
• Are the cable ends OK?

Yes
GO to D6 .

No
INSTALL a new accelerator pedal assembly. REFER to Section 310-02 . TEST the system for normal operation. D6 CHECK CIRCUITS FOR SHORT TO BATTERY

• Key in OFF position. Adjustable Pedal Switch C290
• Disconnect the adjustable pedal switch C290.
• Measure voltage at C290-1 and C290-7.
  
• Is the voltage greater than 0 V at either pin?

Yes
REPAIR the short to battery. TEST the system for normal operation.

No
GO to D7 . D7 CHECK POWER TO SWITCH

• Measure the voltage at C290-2 circuit 490 (RD).
  
• Is the voltage greater than 10 V?

Yes
GO to D8 .

No
REPAIR circuit 490 (RD). TEST the system for normal operation. D8 CHECK GROUND TO SWITCH

• Measure resistance to ground at C290-3 circuit 57 (BK) and C290-6 circuit 57 (BK).
  
• Is the resistance less than 5 ohms at both pins?

Yes
GO to D9 .

No
REPAIR the open circuit. TEST the system for normal operation. D9 TEST SWITCH

• Connect fused jumpers between C290-1 and -2 and between C270-7 and -3.
  
• Does the adjustable pedal motor run in both directions?

Yes
INSTALL a new adjustable pedal switch. TEST the system for normal operation.

No
GO to D10 . D10 CHECK SWITCH-TO-MOTOR CIRCUITS CONTINUITY

• Connect: Adjustable Pedal Switch C290.
• Disconnect: Adjustable Pedal Motor C2001.
• Measure resistance to ground at both pins of the adjustable pedal motor connector, circuits 1494 (RD) and 1495 (WH).
  
• Is the resistance less than 5 ohms at both pins?

  check your battery connections.  A loose terminal when cold can cause this.  Your computer is loosing the adaptives for fuel control.  Because your  car has no accelerator cable, they are two sensors one at the pedal and one at the motor that talk to each other without proper grounding and current they will not work causing limp mode.   When it is in limp mode the car should sound funny almost running poorly.  Sometimes the adaptives need reprogramming.  Good luck.  I need more info

make sure you have the correct spark plugs(2)check the throttle position sensor on the car,as most people would be driving about with the throttle on the floor car feels fine.but as in normal driving anyone only uses the first half of the pedal and this is where most wear takes place and sometimes causes hesitation when driving.best of luck.