ok, so the setup is like this, Engine, Headers, Cats then a cut above the Y-pipe. H-pipe welds here. Finaly true duals. Correct? Also, if this is correct, is it California legal? Also, extreme effects says 2 1/2 HTS. Is that the piping size? According to the tech article, 2.5 is too big. Fourthly, if I'm still using my 4 cats above the y-pipe, i don't need a catted h-pipe, right? And lastly, the true duals have the MAC flowpaths right? I know I must seem like such a newb, but I am completely new to this. Thanx again for everyone's time.