93reefblue347AFR

Ok this is a problem with my 89 GT, when the IAC is pluged in and im driving the carthe RPM's like to hang up between shifts and even if i rev it up in neutral. Now this all started after I did some mods to the car "who would of guessed" I bought the car bone stock and it ran great never had the problem but i deleted the smog system, put headers on it with a no cat X pipe, 75mm TB with EGR but the EGR isblocked off and the harness is plugged with a EGR dumby plug the sends an ok sign the the computer. I unplugged the IAC and the car idle went down so I turned up the idle and the car runs fine the RPM's dont hang up at all. The only problem is on a cold start it idles very low and will die unless i hold the gas at the propper RPM, I only have to do this for about 15-20 sec. then it's fine but am i losing anythig from not having the IAC plugged in? Please give info I did set the TPS pretty sure i did that right at an idle i put it at .99 or so and i dont smell any raw fuel or anything im sure it has to do with the deleting of the smog and EGR system but im not sure