I have a supercharged 03 gt. stock 4r70w with a shift kit and trans cooler and a stallion converter my issue is the OD light flashes when i,m on the interstate. The shop says its a internal problem and it's shifting to late . My question is could the guy that tuned it have changed the shift points for preformance or do I have a bad converter or tranny I would hate to pay the shop to dig into it and find its all in the tune...