Hey guys for what its worth has anyone ever tried to get two exhaust test pipes??? I had them installed on my 300zx several years ago and the the guy at the muffer shop removed my converter and replaced it with a test pipe.... the car was really fast after that... and he drilled and threaded a new place for me to feed my oxygen sensor into it also......The only down fall is you have to put your conveters back on when its time for inspections..... But your crossfire will run a heck of a lot better with out those converters.......And yes its true that a car has to have a certain amount of back pressure but if the test pipes are the same diameter as the converter hook up. power is not robbed........ I plan on getting two test pipes for my Xfire after my inspection this fall......