The Borla exhaust for the PZEV is not smog legal right at the moment,They made a mistake and though that the second cat was a resonator and thus require that you remove it.I have one on my car and it sounds very nice.It is very subtle even with a race header and flex pipe on the car.You should also know that Borla has a center exit exhaust for the PZEV in the works and it looks and sounds great.I have one of those as well.Easy install,great product,2.5" stainless all the way,but still removes one cat.They are currently redesigning the exhaust to keep the second cat.