My check engine light came back on for the po171 code, running lean in B1, S1 again. I replaced the oxygen sensor and I replaced the IAC valve about a month ago and the light is still on. And the idling is still acting crazy when I start the car up in the mourning, it acts like it wants to go up but it don't then the rpms just jumps to 2500 rpm for a second or two then goes to normal idle.(600-800rpm)

What could it be.

I dont plugs wires, front o2 sensor. Upper intake manifold and gasket replaced and fuel filter along with new IAC valve.

Vacuum leak?

I replaced the pvc tube that comes from the pvc valve and plugs into the upper intake. What else involves a vacuum leak, when I replaced that hose I did feel like the car accelerated better than before.

Sorry, I did not realize I put this post in the everything else section. Somebody can put it in the 97-03 grand prix forum section.

vacuum leaks could be anywhere. Spray some water around all vacuum hoses, all around the upper and lower intakes and around the TB, you'll hear the water being sucked in if there is a leak.

whenever I've heard of someone talk about weird idle RPMs on this site, it seems like it always goes back to a vac leak...