If you're going to get a new s-pipe, the 2.5" from W-R would be a much better choice than the huge 3" CXR pipe. I say keep the oem s-pipe and spend the money on other things. The oem s-pipe is 2.25" ID in and 2" ID out with relatively smooth bends. The 1.8" ID crush-bent mid-pipe is the biggest restriction, IMO. If you keep the scuba tank, I'd go with a 2-2.5" mid-pipe and axle-back. Too big and you lose velocity, too small and you add too much restriction. I'd guess that 2.25" ID is probably ideal for a NA 2AZ with basic IHE bolt-ons.

Mouse brought up some very good points about modding in the People's Republic of California. Maybe you should consider skipping the header and get the Tsudo or Strup axle-back instead. Both of them include a larger mid-pipe and you'd still be close enough to legal with both cats still intact that even the Cali SS shouldn't bother you.

 

You meant cat-back right?

 

Indeed I did. Although having 2 cats sometimes makes the typical nomenclature a bit confusing. IIRC some header-back exhaust systems are also called cat-backs. To further add to the confusion, Strup calls their cat-back an axle-back while Tsudo calls theirs a cat-back.

 

Too Funny Fred! That's pretty much it, considering how interesting it is that the governor of california came from Austria.