Well, for the readers here who don't know, the Dynomax kit DOES come with a Y-pipe to replace the forward resonator, then goes into a full 4" system to the end of the tailpipe. And about the Flowmaster system post above the Dynomax one, it connects to the stock 3" pipe AFTER the forward resonator, then into a 3" inlet muffler with (2) 2-1/2" outlets into twin tailpipes to the sides or rear (you get BOTH bent and straight ends in the kit).
Hope this clarifies things