We are proud to introduce the MAD S55 Fat Boy 3.5" Downpipes. These are the largest BMW S55 M2/M3/M4 downpipes on the market. Upgrade from the stock S55 downpipes to the MAD 3.5" S55 catless downpipes for maximum airflow, power, and sound! Upgrade to the MAD BMW 3.5" 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 upgraded turbos. The flex pipe Section will help reduce the stress and unwanted vibration caused by heat and engine Movement.  Features: Compatible with right-hand drive and left-hand drive vehicles Smooth bends for maximum airflow without any drone Up to 30HP increase on the stock turbos, even more on upgraded turbos Lifetime warranty on defects and fitment 90 day return period All orders ship in 1-2 business days Spot on fitment Flex section