I haven't used a C6 but I was looking at a TCI C4. I was told by the local speed shop to stay away from TCI One of the owners has a TCI turbo 400 in his camaro and has had a lot of problems with it . I am using a modified stock C4 now but I will be switching to a race tranny before next season . From all the information I have gathered ,I will be going with a BROADER performance built unit .