700r4 w/ shift kit

Two years ago, I had a shift kit installed to extend the life on my 89 k5 when the shift to second was delayed way too long. With 350,000 miles, it was no surprise, but lack of money for a new tranny and it being my only vehicle, led me to this $200 fix. When I had the tranny rebuilt last year, the rebuilder asked if I wanted to keep the shift kit. I was led to believe the valve bores were worn and the springs would prevent sticking. The shift kit allows a few more RPMs before shift and the transition shift is very smooth. But, when it is cold, just starting out the trans seems to hunt for the proper gear quite smoothly, but shifting up and down more frequently than when it warms up to normal temps. Can anyone explain what is happening, and whether the shift kit is harmful ? Again the shifts are very smooth. Would starting out in (D) rather than (od) help or do I even need to be concerned ? $1800 is hard to come by, and I depend on this vehicle. Thanks to all who have helped in the past. I have learned alot, but transmissions are still beyond my thorough understanding. Black Dog