MexicanPT, I am very glad to hear your system is not reeling it's self back in.[:X]
I feel if we open up the CAT and down pipe to 3" we really do not need a 2.5" all the way back and that the stock exhaust will work with a straight through style muffler. We are removing a lot of the restriction in the exhaust with the downpipe, negating the requirement for the 2.5" exhaust for stage II. The Stage II requirement for 2.5" is only CAT back and retaining the stock CAT!
Remember, you also want to keep the heat in the exhaust because hot gases will flow faster, 3Bar is seeing an improvement with only a 2.25 test pipe! Is he still running a stock exhaust to the back?
Is opening up the o2 housing really going to make that much of a difference? It is only about 4" long and the turbo opening it's self is only 2"?
However, there are several companies making 02 housings that should work with any down pipe and ATP is considering an 02 housing. We should lobby them to make the downpipe fit directly to the stock PT exhaust.
Contact them @
http://www.atpturbo.com/root/navigation/contactus.php
Just my thoughts