I only had the car a few days, and only took it around the block once or twice before I removed the stuff. I really can't say for sure if performance was improved enough to tell. After I removed all of the stuff, I replaced the entire exhaust system, and swapped out the 3.64 diff for a 3.91 diff. So now performance (0-60) is noticeably improved. But I think that main advantage for me is, that it is now easier to work on without all of the smog garbage in the way.