exivic

ok here is the situation, i have a 93 civic, with an ls vtec motor in it. my cars idle is horrible, it fluctuates from 1000 - 3000 rpm's then after it runs for a little while and warms up, it will go from about 900-1500 rpm's I've been told its the iacv. but I've put two different ones on and it did the same thing. but when i unplug it, it idles differently, (the sound kinda reminds me of a quieter muscle car motors rumble.) but i get the check engine light. now the other day we left one IACV bolted on the intake manifold and pluged in another iacv that i had laying around and restarted the car and it did the same thing i dont know what it is. My buddy who is really good with domestic cars says its an electrical problem but im still new to this type of stuff what should i do, or what should i look at doing? any and all help will be much appreciated.