I just started messin w/ tunercat and was wonderin how much PSI will the 4L60E handle. I would like it to tear my head off on the shifts.

 

Max stock programming is 90 from what I have seen (usually only at or close to WOT). Too much pressure can be harmful to the tranny. If you are going to experiment, I would not go over 90 for starters. Remember the power you are wielding with Tunercat. You can cause damage if not careful.