my first question, at what point does the factory exhaust system become a problem? No offense to anyone, but I really do not like the ricer sound of a 4 cylinder with an exhaust, so i would like to keep my factory exhaust system if at all possible. I do plan on installing a test pipe, but other than that, id like to keep it factory. Im going to get a 91 tune for my car for the k03, but my car is getting a few miles on it, and when the turbo goes out, id like to replace it with a k04. Will my k03 tune perform ok with a k04 charger? and are any of the ebay test pipes decent?