Did the problem occur initially (when you first installed the chip)? If not, it's not a tuning issue. The tuning on the chip cannot change over time.
The combination of an aftermarket valve body and a "shift kit" may be causing the issue, but another possibility (thanks to the wide array of valve body changes and subsequent trucks that respond differently to each and every one) is that we may actually need to add pressure to the shifts. Man, I LOVE aftermarket parts.
