I finally got my swap started and it's doing a number of things when it's cold it takes a good minute to get it to finally idle. When it does it surges between 800-3000 rpm. When it starts to warm up it pretty much steady idles at 2500-3000 Rpm. I've tried checking for vacuum leaks by spraying brake parts cleaner around the lines and where the intake meets the head but nothing happend. I blocked the throttle body with a piece of wood while it was running and the motor died. There was a hissing noise Under the intake and I could feel the pressure slowly relieving in the intake. Also when I unplugged th iacv it dropped down between 1000-1500 rpm but it was surging.

 

I just did my own GSR swap and had endless idle/surging issues. I bypassed the FITV which helped a bit, cleaned the IACV which didn't seem to make any difference at all, then on a whim I replaced the throttle body with a different TPS and idles just fine now. Basically check everything then also make sure you've got no air gaps in your cooling.