http://forums.genvibe.com/zerothread?id=25029same problem fixed in that thread.in short, i had the same exact problem, it was intake manifold gasket, TSB available as known defect in 1ZZ engine. I replaced it with felpro gasket even tho i read dealers carry a better gasket. My problem is completely fixed. After sitting overnight outside in 0deg temp, when i start the car, 1700rpm and steady, warms up and drops, rpm is never fluctuating, nor is it jumpy. i took some pics and posted in that thread above. also with a quick how to. good luck, its an easy fix. yohei