I am having trouble figuring out what is going on with my 99 trooper, here is what is up:

Check engine light, went to Autozone to have the codes read.
it came up with P0171 bank 1 and P0174 bank 2.

They told me that it was the 02 sensor on the driver's side and I replaced that-- fifty bucks down the drain and the light came back on the same day.

I have noticed that when I start the engine, it idles really low around 250-500rpm, and sometimes surges like it can't decide what to do in order to keep it running.

I did some more research into the codes and found that a major culprit could be the MAF(mass airflow sensor), so I replaced that and reset the code, but to no avail. it returned pretty quickly.

Now I am reading in some places that it could be leaks in hoses or the Intake manifold gasket.

My question is this: What is the most likely thing, how could I diagnose it, and where can i find information on how to repair whatever it is?

I greatly appreciate any help that you can give me.

Oh yeah, and can anyone recommend a good repair manual, and where the heck to find it? Chiltons has stopped publishing theirs and Haynes doesn't to the best of my knowledge.