I chased a P0171 code for awhile and finally decided that I would refresh most of the fuel system when my 4Runner hit 300k.
I replaced all the vacuum lines first, with silicon ones as recommended by someone here, it didn't fix the problem.
FPR
Newer Charcoal canister (mine had a huge crack)
New O2 and wideband sensors
new injectors and new fuel filter and fuel pump.

Turns out the short rubber fuel line in the tank had a big crack in it and the system would lose pressure after a certain fuel level. Great, problem solved! Nope.
Immediately I started getting a P0172 code and I could smell gas every time I would drive. The truck would drip gas at a stop.

I bought Toyota replacement parts for everything EXCEPT the injectors. Pendejo. I'm guessing one or more of the cheap injectors were stuck open and or not functioning correctly, They were leaking at the fuel rail, the Titanic leaked less than those crappy injectors I bought!

As recommended on here I bought new replacements from motorwestperformance.com and I should have just done that in the first place! One full tank of gas and no leaks and no P0172!

Truck runs great and the fuel system is ready for another 300k!
Lesson learned.

Old injectors are 3 months old, basically fell apart as I was removing them.


New injectors from MotorWestPerformance

Like most vehicle parts you definitely get what you pay for. I'm glad the new injectors solved your issues

The correct thing to do with injectors (in a Toyota, at least) is to remove them, have them serviced by a reputable shop (I have used RC Injection with good luck recently) then re-install. Aftermarket injectors aren't just a crap shoot, they are worse than 300k mile originals.

They generally get clogged from lack of use more than excessive use...

-Charlie

I thought it worth sharing that its well worth ordering quality injectors like what MotorWest offers. 6 months ago I ordered and installed injectors from GB Remanufacturing thinking that they were rebuilt Aisan injector cores, which they are not! They were just cheap generic injectors with no brand name or part number cast on the injector body. My fuel trims were never very good with these GB injectors, like LTFT was -20% and STFT was -10% or worse. Last month I started getting P0172 codes running rich (LTFT got to -34%) and they became more frequent. For basically $120 more, I could have bought the injectors Timmy the Toolman recommended in his injector video from MotorWest. I would not have run into this and saved $220.00. I see others in the 4Runner forums chasing a P0172 and replacing plugs, wires, coils, MAF, O2 sensors, TPS, FPR, and their injectors. I suspect they went the less expensive route I did on the injectors and could possibly be causing their problem. When I pulled 2 of the GB injectors out, the basket at the end stayed in the intake. Just shows what cheap gets you. The injectors MotorWest sells for the 5VZ-FE 3.4L I just installed in my 99 4Runner are Denso which work great and fuel trims are normal again. They not the brown Aisan as MotorWest indicates those had solenoid failures, which is why I replaced my injectors the first time when I had a misfire because one of the Aisan injectors failed. All I had to do was replace the cheap injectors with ones that were quality and that solved my problems. I didnt have to replace all those other sensors which saved me money in the long run.

I've been running the GB reman from rock auto for years and 10k miles (don't drive a lot) with no issues and perfect fuel trims. They also appeared to be oe reman but maybe things have changed since then. Could have just had bad luck and got 1 or 2 bad ones too, heard that's happened before with others.