VCA Notes Story 2 issues back, "Mufflers For Misers" suggested re-using the stock tips. Just cut out the muffler and replace that SECTION with straight pipes. Gain 10-12 HP, sound "better" and real CHEAP-O.
[ PartsRack has other options. We currently have 2 VERY NICE Used 2.5" CORSA complete systems, just traded in on 3". $849.
Go in with a friend and buy BOTH for $825ea and we pay s/h.]