Question on a 1985 Pontiac Parisienne wagon

I recently inherited an '85 Pontiac Parisienne wagon (V8) with only about 100,000 miles on it. It was always garaged and generally only used for such things as road trips on summer vacations, so it appeared to be in amazingly good shape.

Only thing is, it's turned into a maintenance nightmare, over things I

Here's the story:

When I first got it, I was told that "last time it was due for plate renewal, it didn't pass the emissions test - and ended up getting a waiver, so that may need to be looked at". My first guess was that it probably just needed a good tune-up (new spark plugs, etc.), so I took it to a local Firestone dealer and had that done. When they gave it back to me, it was dying at every stop sign or light I came to, once it warmed up (but ran great when still cold). Took it back, and they finally came to the conclusion that while the tech. was cleaning some carbon deposits out of the intake manifold, a chunk of carbon must have fallen down in there and was causing the problem.

Ever since then, it no longer dies at lights, but it seems to be idling too low. My oil light flickers unless I very slightly press on the gas pedal to bump up the RPMs just a little bit, while I'm sitting at a stop sign or light. If I turn on my A/C, it makes a rather nasty grinding/rumbling sound at idle too (which again goes away as soon as I slightly depress the gas pedal).

I took it back again and complained, but they insisted there was nothing else they could do for me, and they "saw the oil light flickering too, but thought it was nothing to worry about".

I didn't have time to mess around with them any more at this point, so I let it go for a while. But then the plates were up for renewal, and sure enough, it failed emissions again! I went to a local mechanic right by my house and told him my story. He promised he'd figure it out. Well, after 4 or 5 trips to the emissions testing place and trying all sorts of things, he finally got it to pass by replacing the catelytic convertor. (He also pulled out the new plugs Firestone had just put in, claiming they used platinum plugs which were inappropriate for this type of vehicle, and swapped them with some regular plugs, and replaced the cap, rotor and wires.)

After all *this*, I *still* have my flickering oil light that nobody seems willing to address, and my rumbling A/C at idle once the engine is warm. And I'm practically convinced it's as easy to fix as making some kind of idle adjustment. Can someone advise me if this is something I can just turn a screw and do myself, or is this going to involve carburetor work or what? It's just not worth dumping more $'s in this thing!

Thanks! (Please reply on this newsgroup as my email listed is a fake.)