PCMperformance.com they are great people to work with, I had them do the tune on my 96 Impala SS. They can tweek shift points, add line pressure to the trans, adjust for different wheels(size) to keep the speedo in line, adjust the fuel map Etc... I know their are other companys out there that also do it, but I have no first hand knowledge of them. Pull up there web site it gives alot more detail. Alex is good people. - Lance