I had a magnaflow trux welded in my dual setup prior to the turbo. Others have gotten GT take off H pipes and had them fabbed in. JBA and Magnaflow makes a reverse Y kit. JBA also makes a H pipe kit as well.

 

I didn't know but if you look at the pics above, Saleen sent a "Y" pipe with the pipes and muffler....

I personally would build an "X" with the stock Y and the Saleen Y.... But I guess there are a few options out there.....