The Interceptor IS for spirited driving and should not take more than a few days to dial in but it's job IS to make the shifts harder. The hard clunky shifts here are indicative of an Interceptor not plugged in all the way or a pin pushed back. Yes, you should always take of ANY mod that the dealer can blame for ANY problem. There have been NO confirmed (and this is the first mention) of trannys being destroyed by the Inteceptor and the company that makes them would NOT be as successful as they are if their products blew up customer's stuff. See the Magnuson Moss Act for info on aftermarket products and warranty. And if you have a problem with something you got from me, contact me directly for assistance instead of waiting for something to happen - I use EVERYTHING I offer EVERY day.