the test pipe or removal of a catalytic converter from a car in which is not under a rebuilt, antique, project, or salvage title will not only fail emissions (since they type your car make and model into a computer and if you are sending out more carbon (which you will be) than what is on the readout, they will put a red sticker on your window). On sites that sell test pipes they most likely have a "for off road use only". finally when I asked my mechanic he said it was illegal and unethical with the chance of fines/and or legal prosecution and liability if a licensed shop removes catalytic converters from a vehicle. finally # 2, cops have the right to look in your hood and under your car if they beleive you are running illegal modifications as well as they will reference the VIN # to make sure your engine belongs in your car. (not that speeds are doing swaps yet that i know of) thats all i know to keep you out of trouble.