Replacing your catalytic converter with a CAT by-pass pipe yields an instant horsepower increase. Recommended for racing applications, the by-pass pipe replaces the constricting catalytic converter with a free-er flowing exhaust pipe. Available in black painted steel, or shiny stainless steel. Note that the use of these pipes is legal for off-road use only in most states.
Bursch Steel Cat By-Pass, with Oxygen Sensor, 911 (1978-89)