2003 corolla P0171 error please help!

[aku5]

I am about to pull out my hair because im not able to find this problem and its been almost 4 months. The first time i went to a mechanic they got a p0171 lean code so they replaced the gas cap but that didnt work after about few days of driving it came back on so they replaced the MAF sensor and 02 sensors then after a few miles it came back on. I took it back and got my fuel pump tested and a smoke test but they found nothing wrong. but my CEL came back on.  THEN  i replaced my intake manifold gasket replaced along with the two vacuum hose, and  purge valve next to the air box and throttle body seal replaced. fast forward a few weeks while on the freeway my engine started to shake they found that i had a misfire in my cylinder one so i got my spark plugs replaced, ignition coil for cylinder one replaced, valve cover gasket replaced. I asked them that if that could be a problem that causes P0171 they said its possible but after a few weeks THE SAME CODE CAME BACK!!! PLEASE HELPPP its driving me crazy

[oldcodger]

Hi,

Your Mechanic / garage, is it an independent garage or a Full Toyota dealer.

Do they have a full array of diagnostic test equipment ?

It might be worth paying for a diagnostic test on the machines at a Toyota dealer, though no guarantee they will find the root cause.

Does the engine run differently when the checklight comes on ?

Do the plugs show any signs of lean running?

https://www.tuningmatters.com/how-tos/beginners-guides/check-spark-plug-correct-carburetor-setting/

Anyone checked out the injectors ?

What engine do you have, sounds like you are not in the UK ?

[aku5]

I got back from the dealership today and they checked my fuel injectors and they said its the problem because it is causing my fuel trims to be at 30% and he said its suppose to be at 10% im not sure if he said it was long or short term fuel trims or if that matter. They would charge me 1,300 but i had to decline because that was kinda outrageous so im just going to take a independent garage to get it fixed 

[aku5]

I have not had any noticeable driving performance when the engine light is on.

[scott2006]

UNDO THE PCV valve AND CHECK FOR A VACUUM. when THE ENGINE IS RUNNING  IF NOT REPLACE THE VALVE ON SOME THE EXHAUST INLET GASKET NEEDS REPLACING.