skunk2 makes a 70mm test pipe its only got 1 02 bung though

 

to put things into perspective for you

Stock cat and exhaust has an inside diameter of 60mm. if you wish to get a test pipe wit the same diameter as the stock exhaust, then get the 60mm. it will already give you gains since the stock cat has restrictions inside it as you can see. if you have upcoming plans on modding the car, get the 63.5mm or 70mm.

Though, IMHO, a 63.5mm test pipe would be the best application for an N/A car. That was my 1st mod and it was just a custom one. I honestly didn't feel any gain however i didn't feel any "bottlenecking" as well. BUTT DYNO wise. Atleast, when you get the 63.5mm it will still be applicable if you get a bigger aftermarket exhaust. I even heard on a build here somewhere that a 63.5mm test pipe connected to a single 70mm exhaust will give you better mid range gains than a straight through 70mm one. ill try to look for that thread. they have the dyno numbers and it was tuned via engine management so i guess its reliable.

but then again, each mod will react differently to each car. but i'm just stating my opinion. HTH