Engine Idle Problem, Not like any posted before. Options

[Kadett]

I got this very strange problem. Car already been to the garage 3 times(toyota dealer). Still i have this problem (at least with a warm engine)

It started out like this:
1 day i started the engine (cold) and it would idle at about 1100 RPM(when i bought the car, it was 1500-1700 i think) . When i increase the throttle it would do that like normal but then it would go below its idle RPM (cold about 1400??) to about 400 and lower and sounded like a choking sound (to much fuel) and sometimes die on me.
When the engine is warm it would idle normal at 800rpm. And when I increase the throttle then it would go to about 3000 and let it drop it would go to 600 and then go back up to 800-900 rpm.

Theres a part already replaced (literal translation= Step engine) controls the air mixture with a cold/warm engine or something like that. Have not tested it with a complete cold engine but when i started it at the garage (engine not running for about 2-3 hours) it idled at about 1400 rpm. GREAT i said. Problem solved.

But after test driving it, it actually sometimes drops below 800 RPM again.
OOOOOOOH I am so frustrated. Plz somebody what can it be, before i push the f*&^%g car of a cliff!!!!!!

EDIT: I forgot to mention something: When the car idles at 800 and i have the lights/brake on and then turn the lights of or let go of the brake the rev go up about 50-75 rpm. Related?

This post has been edited by Kadett: Jun 7, 2005 - 10:00 AM