I used to build exhaust systems in my youth TIG is the best but expensive, MIG is ok for the rough

 

Finally broke down and called APR to get a tech on the phone.
2.5", straight through, for their model as well......

Done.

I'm buying their version for $230 and slapping it on the car.

 

Test pipes are great, but in my car it was nearly impossible to install ( Four hours), and you need a new ecu tune

Go with the 2.5

 

yeah, my mate can TIG weld, so he makes all his own exhausts.. Some of them sound so angry its awesome.. But he can't weld stainless steel to well. i want a stainless exhaust. they look and sound good!

 

would running a test pipe fail you for CA emissions?

 

I would think so, even with a spacer for the secondary o2 sensor your not going to pass..

when i made mine i just did 2.5" becasue we did a custom eghuast and i just had 2.5" tubing so i just used that for everything..

is there really and large benifit to anything any bigger?