I've driven about 500 miles since getting my 2000 GTP, after having it completely serviced by the local GM dealer, to include a complete transmission flush and new filter. The car shifts perfectly under normal driving conditions and in normal shift mode, but part of my commute is through DC traffic and at partial trottle. Under some conditions the transmission is very slow in shifting between 1st and 2nd, and 2nd and 3rd. Using Performance Shift mode eliminates this but I'm not sure if using Performance Mode in commute traffic is OK. I've researched some alternatives:
a) Reprogramming the computer to alter shift points. This approach always seems to requires the use of Premium fuel which is not an option.
b) Installing a shift kit like the one offered by 3800performance.com, the Thrasher 4T65E Shift Kit which uses a dual spring setup and precision height shims which are placed inside the 1-2 and the 2-3 accumulators.
Are any of you familiar with what I describe or has anyone installed such a kit in their GTP transmission. If so, what changes have you seen in both normal and Performance shift modes?