I know its a common problem with these things, but figured I'd check anyway. I've got an 02 alero with a hybrid 2.2 I built. it's all factory parts, runs great, but has intermittent p0171 with bad surging at idle. likes to stall out, hard to start. fuel trim goes max to the plus side,
o2 still sits around 80mV. doesnt seem to have any vac leaks, no maf, new fuel pump with great pressure even when concern is there. it comes and goes, so I can't seem to pin point it yet.

 

Check very well for vac leaks. If thats not it, it can also be a bad MAF sensor. I would spray it with some throttle body or brake clean and see what that does before I actually replaced it. Sometimes they just get dirty.

 

doesn't have a maf. checked for vac leaks with water and with brake cleans. found nothing. concern hasn't come back lately. for now i suspect small debris in the fuel rail and injectors since i had it apart several times, finally passed or flushed out i guess.