Parts & Accessories We supply various different fuel rail adapter couplings, wiring harness adaptors, manifold adaptors and o-rings for all different applications. Below are a selection of the fuel rail and manifold adapter caps that we can supply: We sell replacement O-rings for various applications. Below are the O-rings that fit our ASNU performance injectors and associated fuel rail couplings: We offer various different harness adapters to fit our ASNU performance injectors into your existing application. These are listed below: