RB N54/N55 5/16" Thick Head Flange with Inserts 320i (F31) If you're running E85 or

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

If you want extra ordinary performance buy air intake also

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

it does not block exhaust flow as the resonator is only around the downpipe

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

RB N54/N55 5/16" Thick Head Flange with Inserts 320i (F31) If you're running E85 orThese 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