i am about to put a cat back exhaust on my 2001 180 quatro. i have not been able to find anything about the performance gain of a down pipe. neuspeed makes a 60mm downpipe but im not even sure if it fits the quatro, i dont see why not? if i am going to add one i would like to do it the same time i am putting an exhaust on. if anyone has put one on please let me know if its worth the money. or if anyone knows why no one seems to have them. i installed them on my 91 300zx tt and you could really tell a difference, reduced turbo lage and really opened up the top in. looking for any advice. thanks