The P0171 code is for a Lean condition which is why I suspect that you are looking for a vacuum leak. What tests have you performed and what parts have you replaced?
I already know the code and what it stands for. I had this in my original question. I have replaced fuel filter and o2 sensor in front of catalytic. I had toyota and a mechanis say it sounds like a vac leak on the passenger side / bank 1. i am looking for help on identifying (location) of leak.
Have you checked the MAF sensor for debris on the wires yet?
yes, did not find anything
With the engine running, have you tried spaying carb cleaner in and around the intake area?
That will be the next item to check. What you will want to do is when it is cold, use some carb cleaner (anything spay flammable that will not damage your 4Runner) and direct it toward each area of the intake and listen for any changes in the way it idles. If it has a vacuum leak, it will suck in the spray and idle up higher. That will give you and idea of where the leak is occurring and then you can tear it down to inspect.
We don't have many of these issues but when the P0171 is present, most often it is the MAF sensor. I know you checked it and found it good.
Do you still need help?
This sounds just like a MAF problem. In addition to the check listed above, I would replace the MAF, clear the code and retest drive it. It will probably make one heck of a difference. Please only use OEM Toyota MAF sensor.
Thanks i willtry but do you think it might be the rear o2 sensor (behind catalytic)?
No, please do not waste you hard earned money on replacing the O2 sensor, it will not fix this issue.