Error code po171

the p0300--p0301-p0302=p0303 are misfire codes and can mean needs tune up or wiring problem and p0171 is system to lean bank 1 with this code if you correct it will probably correct the misfire codes your receiving
http://www.obd-codes.com/p0171 Fixing Hesitating Car P0171 Code YouTube P0171 System Too Lean Bank 1

2000 Toyota Corolla, P0171 & P0420 codes - YouTube

? 5:43
https://www.youtube.com/watch?v=ahJnJ19-vwY
Jun 13, 2011 - Uploaded by StandardBrandParts
Standard Motor Products presents: Technician's Toolbox "2000Toyota Corolla, P0171 & P0420 codes"

Smoke testing for codes P0171 P0174 - YouTube

? 5:48
https://www.youtube.com/watch?v=kZsqEfP-5zM
Jan 18, 2011 - Uploaded by realfixesrealfast
These two codes mean a V style engine is running lean on both banks. So you have to be thinking - what can ...

How to repair fault code P0171 and reset warning light ...

? 26:31
https://www.youtube.com/watch?v=Y8FBGrCT3rM
Nov 27, 2014 - Uploaded by Peter Finn
How to repair and fix fault or error code P0171 and reset warning light Toyota Corolla VVT-i engine. ... Also how to find fault codeusing OBD scanner. ... Trouble shooting a misfire, Code P0300, P0301, P0302, P0303, P0304, P0305, P0306, ... 2000 Toyota Corolla, P0171 & P0420 codes - Duration: 5:43. by ...

P0300-p0304 misfire on cylinder 1-4
P1399 random cylinder misfire

P0171 System Too Lean (Bank 1)
P0174 System Too Lean (Bank 2)
P0301 Cylinder #1 Misfire Detected
P0302 Cylinder #2 Misfire Detected
P0304 Cylinder #4 Misfire Detected
P0306 Cylinder #6 Misfire Detected

Nothing to your car, just the environment.

Have you had somebody clear the codes after you installed the parts.If not the codes have to be erased by using a scan tool.

P0171 is a lean oxygen sensor code. Codes P0300, P0302 and P0304 are all cylinder misfire codes. Low fuel pressure can cause all of these codes and would be the first thing I would check before replacing anything. Lean codes can be caused by misfiring cylinders. Engines running lean can cause misfires. So you have to figure out which came first - the lean condition or the misfire. Also, it needs to be verified that the engine actually is running lean and the oxygen sensor is not "lying" to the computer. An oxygen sensor that is a liar can actually cause the engine to run rich while telling the computer that it is running lean...AND THIS can cause misfires.

P0420 Is an evaporative emissions system leak code. This code is most often caused by a bad or loose fuel cap. It is also often caused by people refueling their vehicles with the engine running. It can also be caused by a leak in the system that has nothing to do with the fuel cap or refueling.

Evaporative Emissions Vent Solenoid failures are very common on Toyotas and can also cause P0420.

So, to wrap all of this up in simple terms:
You need to get some diagnostics done to save you from wasting a bunch of your hard-earned cash trying to guess what to do to fix the car.

All those codes mean a specific cylinder missfire. Start with tune up. Plugs, wires & air & fuel filters.

have you changed the spark plugs? also any OBD code after fixing the above?