Save your money. Unless you're running an aftermarket cam with some added overlap, you'll pickup about zip in HP.
If you do go ahead with it, expect to cut off the factory down tubes in front of the cat and have flanges welded on to mate to the header. This kills your ability to go back to factory. Or, if you are no subject to emissions tests a better solution would be to not cut the factory system and have a 'track pipe' made that connects the headers to the exhaust system post cat.
Jeff <-- RD headers with a MM 3.7 engine.
Last edited by Jeff N.; 11-21-2007 at 10:43 PM.
Bellevue WA
90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
86 Porsche 951 - Track Toy