Throttle / Idle problem

I have a 1988 Cavalier Z24 2.8L Multi-Port Fuel Injection. I've noticed that when im driving, let off the throttle and push the clutch, my rpms seem to stick for a few seconds, then slowly drop... they sometimes stop around 2,000 for a second, then slowly go down again... Also, sometimes when i do this they will drop rapidly to normal idle, then shoot up to about 2,000 again...its confusing me as to what it is... i've been told throttle body, mass air flow sensor, idle air control valve, throttle position sensor... some advice on where to start looking and what i need to do / replace would be great :) oh and also, if i put it in 5th gear and floor it, then let off the throttle, it seems to keep accelerating for a few seconds, then stops.... or if i push the clutch in, the rpms actually increase, like something is sticking... but its weird how sometimes it drops to normal idle and immediately shoots up again...??? lost

It does sound like a sticking Idle Air Control pintle sticking sticking, but I'm not saying to replace it. I have gotten away with taking the IAC off, spraying it thoroughly with blake cleaner, waiting for it to dry, then spraying again with wd40, PB Blaster or some lubricant. You could even try working the plunger up and down.