Umm... the throttle body doesn't have a "manual" idle screws. Those are to help set the IAC count, which needs to be in a specific range. You cannot adjust the FiTech like a carb. You'll never get it right.
I HIGHLY recommend you check out this thread on Chevelles.com as it's the best FiTech tread on the web at this point. Actually the whole EFI area has the most info on this unit and the Sniper.
http://www.chevelles.com/forums/89-e...tings-etc.html