4L60E Problem
You can also disconnect the MAF; if that cures the problem you know you have a MAF problem. Make sure there is no vacuum leak around the MAP and that the TPS connections are tight with no corrosion.
After that, I would hook up a pressure gauge to the trans and watch the pressure during the shifting problem.
You could also remove the servo to replace the seals. While rebuilding the servo is easy, it is difficult to remove the servo in an F-body - the rear of the trans has to be dropped quite far to make room for the servo removal.
Just some ideas for you to think about.





