RB N54/N55 5/16" Thick Head Flange with Inserts 320i (F31) we offer a catless version

we offer a catless version which incorporates a 4" Resonator in place of the catalyst

Installation is very discrete

Each set is 100% custom-designed from the ground up

the intake system delivers a louder and sportier induction tone that perfectly complements tuned and hybrid turbo applications

If you're running E85 or ethanol mixes in your S55 BMW

RB N54/N55 5/16" Thick Head Flange with Inserts 320i (F31) we offer a catless versionThese flanges are designed with true tapered inlets and backside stress channels (as they were from the OEM's). They are a 7 piece design (single main 5 16" thick flange, six exhaust runner inserts with locators for 1 1 4 Schedule 10 Weld Els). Unlike competitive products priced comparably and made from cheap material, these are billet machined from 100% 304 304L material (with certs). The proclaimed flange of choice for many educated N54 N55 turbo