I had the exact opposite thing happen with mine. The Greddy Evolution exhaust I bought back in 97 went fubar on me. In 2001 the mesh resonator inside the muffler portion came off its weld points and was moving free inside the muffler and creating a hella rattle. The local shop I bought it from said there was only a 3 year warranty on it and I was out of luck. I called Greddy directly and they asked me to send them some pics of the exhaust on the car, a few shots up the exhaust pipe to show the resonator had dropped, and my proof of purchase. I had lost my proof of purchase and the shop had purged it from their system since it was 4 years old. Greddy gave me NO problems about it and shipped a new exahust (full cat back, not just the muffler) to the shop and had them install it and paid for shipping on both the old and new exhaust, as well as the install. Total turn around time was less than 10 days.

Needless to say I highly recommend Greddy and their exhaust products. I even put a sticker on my back window for them (even though I despise most ricey stickers) since they took such good care of me. I don't mind giving a little free advertising when a company takes good care of me and stands behind their product.