ACTIVE AUTOWERKE BMW EXHAUST STUBBIES FOR E9X M3You already own the Active Autowerke Signature Series X pipe for your BMW E9x M3 to achieve the maximum in performance and power, but were limited only to the race track since it replaces the BMW factory exhaust catalysts and was not intended for the highways. The Active Autowerke Stubbies is designed primarily as a cost effective means of utilizing your existing BMW Factory catalysts into something usable. If this can be done, then there is No need