Thanks guys. Its from a 91 LS400. The engine ran flawlessly before pulling it out. After pulling it out, I blocked off the EGR exhaust port since I will be removing all emissions components in the future. The EGR stuff is still on the engine. Could this be causing my cold idle issues?
When trying to start the engine cold, the engine will idle at like 400 for a split second and cut out and die as if the computer is cutting the spark.
After letting the engine warm up a bit (holding peddle at 1200rpm for a minute or two) it idles solid at 550rpm. The day before it would idle at 700 once warm so maybe temperature is playing a roll?
I tried unplugging the IAC plug when it was warm and idling at 550rpm. There was no difference in rpm. I put my thumb over the tube and felt vacuum. The vacuum was the same strength with and without the IAC plugged in. The IAC should be good since it was fine before pulling the engine out but it could possibly be bad.
Tomorrow morning I will be getting an exhaust installed so The o2 sensors will be hooked up. Hopefully that will solve my problem.