[kjewer1]

Any time idle is surging you are hitting the coasting fuel cut RPM limit. It is around 1600 rpm too IIRC. Essentially the car is trying to idle higher than 1600 rpm, but the ECU completely cuts fuel (coasting fuel cut) making it drop. When it clears the hysterisis limit it revs back up, and the cycle continues. Find the cause of the high idle (EGR, ISC, FIAV, BISS, vac leaks, throttle cable, lunar eclipse, etc) and you will likely have found the cause of the surging. With DSMlink you can raise the coasting FC limit, but that just gets you around the problem without really fixing it. There are times when it's necessary though.