Is there something I need to measure? Or would either a 60/70mm both bolt up? I have the OEM currently on and was just wondering. My cat is sounding like it has rocks in it and I figured instead of a OEM replacement, I'll opt for a test pipe and spend the remainder that I would of on a slight tune.

So is there an issue with going bigger?

 

OEM is 60mm. Some test pipes come in 63mm, which is fine. Don't get a 70mm.

 

Always get the size that matches the exhaust pipe to keep a smoother flow. ..at least that's what I gather from reading Gernbys thread on his exhaust. Although you probably wont see anything positive or negative unless its dynoed

 

^that. If you have the OEM exhaust, you can go with the 60mm or 63mm.

 

Thanks guys....I'm guessing I only go 70 if I'm boosted with a 3" tube all the way back.

 

Yes, 70mm would be the desired choice if you're running anything other than a stock exhaust (70mm is 2-3/4"), and the 60mm would be the choice if you're running a stock exhaust.