1990 Firebird V6 Rough Idle

Hi, I'm a do it yourselfer and fix everything out of books and online
info but I'm stuck with this problem.

I can't figure out why my car is rough when in idle, like anytime the
car is on but not moving, like in park or a stop light or just anytime
i'm not pressing on the gas.

The minute I step on the gas the car runs great but when I'm
stationary(not moving) the engine shakes alot.

It's not the spark plugs, they're in the right place.

I dont know anything about the Rough Idle Valve, it's a tiny little
piece of plastic I don't know how that could have such a big affect in
the engine.

Any ideas anybody?

Thanks and please don't respond with a quick 'fix that and bam than you sam' because I have no idea what I'm doing nor do I even know the terminology for most parts.

And any smartasses that want to respond with take it to a a mechanic, well thanks, but I dont have the money nor the want. I really want to learn how to work on my car.

Thanks!

Ismael

Sounds like it could be your IAC (Idle Air Control) sensor