MAD BMW S55 Downpipes M2C M3 M4 W/ Flex SectionUpgrade from the stock S55 downpipes to the MAD S55 catless downpipes for maximum airflow, power, and sound! Upgrade to the MAD BMW S55 downpipes to eliminate the backpressure caused by your stock catalytic converters. By upgrading to our downpipes, your turbos can now spool faster and achieve maximum power. As a bonus, your car will sound a lot nicer as well. Expect up to a 30HP increase on a tuned BMW S55 with stock turbos, even more on cars with