I don't know about the Greddy exhaust. I think some of their models have a ricey sound which is why I would stay away from Greddy exhaust. Plus, I hate their muffler design. Magnaflow, Flowmasters are the ones I really recommend. I don't know about Injen quality, but the look nice and sounds pretty good too. But if you want better performance, get a cat-back over an axle-back exhaust system.