i have an 03 lb7 it already has a 4 inch turbo back exaust or at least down pipe back. does any one know where i can get a performance down pipe or if i need one? my truck also has a western performance chip i think its kind of weak. i recently purchased the banks ram air intake system also. i thought my transmission was going bad because if i floor it in 2nd and 3rd gear the truck will sit at about 3k rpms and when i let off it will shift any sugguestions the truck has 131k on it i want to make it faster my buddys hemi beats me pretty bad with my truck shifting funny and its kind of embaressing help please