I'm normally not a big supporter of "mechanic-in-a-can", but, on a suggestion from this forum, I tried the Lucas FI system cleaner. I have one of the pressurized FI cleaners, but I haven't gotten to the GM dealer to get some of the good stuff they use. I picked up some Lucas before last fill up and there is a noticeable difference in idle smoothness, throttle response and acceleration.
Good stuff.
Good stuff.