I'm pretty sure the downpipe that comes with the kit is 3", but I could be wrong. I'm not aware that APS sells bigger downpipes. I know they sell the 3.5" test pipes tho.

No the SFR just goes after the cats. Replaces the y-pipe and uses a true dual setup. I'm keeping my cats for emission purposes.

You might see similar gains with the APS 3" true dual though, since that's recently released which includes 3.5" test pipes.

 

The APS 3.5" test pipes replace the downpipes and connect directly to the 4-bolt flanges of the turbos. That's why I was curious if you were considering them. But since you have emissions to worry about then they wouldn't be a good idea for you. Anyhow, thanks for the info man and your ride is badass.