BLACKMAGIC,
Any professional mechanic caught removing ANY of the emmissions controls, including the cats, faces very heavy fines, and possibly criminal prosecution from the federal government, and most state governments also.
You can do anything you want to your vehicle, but the State does not have to allow you on the roads. A drivers license is a privlege, not a right. The same is true for the plates.
If you want to use the car "off road", you will have no problem as long as you do not put the car on a public road.
Lets set all the legal issues aside. If you do the research, you will find that street car owners who occasionally race their cars have found that they do better with the stock system in place.
5.0 Mustang owners have found that the designed back preasure created by the cats gives them better low end torque for the launch. They get better speed without the cats, but end up with higher ETs (Elapsed times). ETs win the race with very few exceptions.
The feedback system provide driveability and fuel economy advantages. Their ability to continuously fine-tune the air fuel mixture to match different conditions, even different fuels, is dependent on the back pressure as designed WITH THE CATS.
The computer maps of air-fuel ratios AND timing are set for the exaust-system back-pressure of the stock exaust with the converters.
Clearly, you will gain nothing by removing the converters, or gutting them. You can get more horsepower with some "bolt-on" items, but again, if the "bolt on" item does not have federal EPA exemption, and usually State exemption, the car will not be street legal. (= no plates)
What you do to your car in your own back yard is your business. When you put it on the public roads it is the public's business, and the "public" has decided it wants clean air. rangerj
