So I've been having this problem in my truck for a while (1996 c1500 5.7). It tries to rev itself, or push the rpm's, even if the truck is stopped. It doesn't matter what gear it's in, but if I have it in D, at a red light or something, when it happens it actually pushes the truck like I'm on the throttle. I've been told it could be a bunch of things, already checked/replaced TPS, spark plugs and wires, a few things like that.
Last night is when I did the plugs. When I started the truck to check how everything was working, as far as the plugs go, it was all good. Then it did the revving thing again, only I was able to hear that it was actually moving something. A while back I thought it had to move the butterfly up and down to actually do it, but I realized it wasn't. This time I could actually see it all. What I eventually found is that what moves is the pulley on the AC compressor. As it spins for 1 or maybe 2 seconds, the rpm's shoot right up, then it stops and everything is normal again for a minute until it goes again.
I don't see how the two can even be connected, but maybe that's just my ignorance. I've done a lot, but never much with AC's or the compressor. A brand new compressor can be a bout $200 at the low end. I need to fix whatever makes this happen but I need to know how to check/what to look for to know for sure.

 

Have you tried cleaning the IAC = Idle Air Control ? this controls the idle.
I don't know the specifics but I believe the IAC is also tied in with the AC so that the engine will come up a few hundred RPM to compensate for the AC running...