This reply maybe way too late to help you, as you posted in March of 2012 and this is April of 2015, but maybe it will help someone else. I own a 98 CL 3.0. I experienced the same problem after removing my intake manifold to clean the EGR passage. After reinstalling the manifold, I began to experience this same surge (also called a "hunting idle"). I discovered it was indeed the IACV located beneath the throttle body (on the 3.0). I tried cleaning it with brake cleaner to no avail. I ended up purchasing a new one (ebay_ not too expensive) installed it and I have not had the problem since. Word of caution: If you intend to do this install yourself, be very careful removing the two screws that attach it to the throttle body as the heads of these screws have very soft heads and are easily damaged. Hope this helps somebody. BLACKACPILOT_Out!