[ChevyTech]

First thing I would do is check and double check the firing order to make sure you did not get two plug wires crossed.

Another thing I would check is to make sure the EGR is not stuck open a little ways.

Even with problems the system should be opening up the IAC to speed up the idle.

Make sure the ground wire on the back of the passenger side cylinder head is in place. Also make sure the ground wires at the front of the intake are all getting a good connection. The computer and the sensor circuits through the computer connect to ground at the grounds in the thermostat area.