The aFe Power cat-delete, race down-pipes eliminate the catalytic converters for maximum exhaust flow for the popular BMW 1 series and 3 series with the N54 twin turbo motor. In recent dynamo testing, these race pipes produced 17 horsepower and 32 pounds x feet torque over the factory down-pipes. These high performance race pipes are constructed out of lightweight, TIG-welded, 3 inch, brushed finish, 304 stainless steel and use thick 3/8 inch 304 stainless steel flanges for a leak-free seal and a factory fit. All aFe Power exhaust systems are engineered and manufactured in the Corona, California manufacturing facility. Tig-welded: 100 percent TIG-welded by certified craftsmen for race proven strength and durability. TIG-welding provides the strongest welds reducing stress cracks. Factory O2 sensor locations: These down-pipes use factory mounting locations for the O2 sensors. Hassle free installation: All hardware and brackets are included for a hassle free installation. Note: This is a race only product used solely for competition. Its use is limited to closed course and open course racing that is formally sanctioned by a recognized racing organization. Any other use including recreational off-road use could be in violation of local, state and federal laws. A check engine light will emit and aFe Power recommends using a programmer but it is not necessary. Also fits: BMW 335iS L6 3.0 liter, 1 Series M Coupe L6-3.0 liter.