Dude, the piping is 60mm which in inches comes out to 2.375" so go with either a 2.25" or 2.5" cat. A universal cat will work out okay and the $$$ you save can be used to have a decent muffler shop make it a custom fit and I bet you'll still come in under the cost of a direct fit. The only question I have is are you going with a smog legal unit or actual straight thru. Whatever you choose universal, direct fit, carsound or Random, any and all will still flow better than stock. The only thing that should sway your decision is the ultimate final plan for the car. Don't buy something to get you by right now, go with the part that fits into your overall plan and you won't have to worry about it later.