hey, i got a 2000 GSR. it idles funny, randomly from 2000rpm to less than 500rpm. it doesnt fluctuate, just randomly. seems to happen after driving for a while. bad iavc? if so, what years could fit? its a 2000 b18c1 running a 98obd2a ecu. could it be a bad ecu? any help is appreciated.

thanks.