Active Autowerke Downpipes with Aflow Cats – G87 M2 | G80 M3 | G82 M4 (S58)No tune needed. No CEL. Built for power. The Active Autowerke Aflow Downpipes replace the restrictive factory units on your S58 powered BMW, freeing up horsepower, sharpening throttle response, and adding a deeper, more aggressive exhaust tone all while staying emissions compliant in 49 states. Made from 304 stainless steel, these 3 TIG welded downpipes feature 4. 5 high flow Aflow catalytic converters rated for up to 800 HP. The design minimizes back