Idle Fluctuations.. Bad IAC? Manifold leak? 13B NA
 

Just got the car up & running today. This was an issue before Winter hit. On cold start it maintains around 1000RPM and after warming up it bounces back & forth from around 100RPM to 1000RPM. Engine starts to shake as if it's stalling but never does when it drops. As soon as the idle drops, it spikes it back to 1k. Not sure if it's an air leak or bad IAC or something else. Any info helps.