i did, cai, flowmaster weld-in, 4.10 gears, t-lok and basic flash tune to my 03 v6 auto. i did notice a small increase in throttle response from the cai, (BBK btw) and a very nice almost GT-like exhaust note from the flowmaster. the best thing you can do, is the 4.10 gears if you are auto. while you are in the rear end, you definitly need to put in the t-lok. and since you will need a speedo recalibration, get a base, if custom tune. after all that stuff, i was able to spin the tires for a few feet, by goin wot right off the bat, and chirp 2nd when it shifted. by the time i was done with those stage 1 bolt-ons, it felt like a different car. sry for the run-on sentances, its just how i type in thought.