VRSF Ceramic Catted Downpipe BMW 135i 335i N55 10-13The VRSF 3. 5 catted downpipe upgrade is THE best bang for the buck mod available for your N55 135i & 335i xi. By eliminating the restrictive catalytic converter in the factory downpipe, back pressure is significantly reduced which results in faster spool, an increase in power & a more aggressive exhaust note. Our downpipe also features a unique CFD optimized cast merge collector which offers the smoothest turbo to mid pipe transition available. Every