My $.02
I swapped my Yodude and stock SVT back and forth about 4 times, to see/feel the difference, and in my humble opinion, the exhaust restriction is not found in the back half of the system. I mean the dude flows freely (very) but the gains were just not that noticeable (yeah, I know..the more mods the more gain yada yada yada). I really feel that if you look at the design of the manifolds/pre-cats and stock Y, you can't help but come to the conclusion that they are the major restriction. Even if you mystery-mod the set-up, you still have terrible flow characteristics compared to the headers. And...a good cat-back is anywhere from $340-600. A good Y is $149-249. Add that together, and then compare the cost to the headers which come with a good Y. I think the headers are the smarter buy by far.
