Ok spent the day trying to figure out why a Toyota rav4 was running lean, P0171, bank one lean, P0174 bank 2 lean, car has 200K on it so the possibilities are endless. usually the MAF (Mass Air Flow) sensor is what causes both banks to go lean, or a vacuum leak. In this case I checked freeze frame date, the lean condition happens when car is warm, and driving at cruise speed, this rules out the vacuum leak, vacuum leak would flag the code at idle. so it is clear I have a MAF issue. got the part from an aftermarket supplier, installed, test drove car, still lean at cruise, came back to shop, checked fuel pressure and checked fuel volume, thinking maybe at 200K the pump is going bad. Not the case, everything looked great. Ok maybe restricted injectors, so did an injector cleaning to no avail, so I decided to get another MAF, since I am not a big fan of aftermarket parts. Installed 2nd MAF. same thing only this time the car falls flat on its face during accell, WTH!!! Ok enough is enough, after several more hours of checking, I decided to get an OE MAF. Installed and drove car. Ahhhh, fixed, runs great and no more lean at cruise. Lesson learned once again, only OE parts, the problem is I work at a shop where the intelligent level is not very high. Oh I forgot to mention the OE part cost less. So a wasted day chasing bad parts, and the good parts was less than the aftermarket junk part.