I've searched through the forums here and read just about every thread on the Integra's surging. I've tried pretty much all the solutions listed and nothing has helped.

I have a 99 GS-R that surges pretty bad when it's warm. All the threads here point to a failing IAC. I replaced mine with a new factory unit and it still surges, and no CELs. So out of curiosity I unplugged my new IAC(leaving it bolted in place) and plugged my old one in so I wouldn't get a CEL. I started the car and held the throttle till it warmed up, and it started surging when I released the throttle. So why would it be surging without the IAC actually moving and adjusting the engine speed? Would that kinda tell me I have a vacuum leak?

 

Could be a vacuum leak and you've already checked the iacv. I would have said to look into the EGR valve but that's only in automatics. Check all your hoses and make sure none are disconnected. Also look into your spark plugs, spark plug wires, and dist. cap/rotor.