MACE 6.35MM MANIFOLD INSULATOR TO SUIT NISSAN SKYLINE R33 RB25DE RB25DET TURBO 2.5L I6Exclusive to Mace Engineering, here we have our design registered manifold insulator to suit the Nissan Skyline R33 series, fitted with the RB25 I6 engines. What are manifold insulators and what do they do? Manifold insulators are a thermal insulating spacer that mount between your engine block and intake manifold. Made from a heat blocking composite, our manifold insulators will increase power from your engine by keeping the intake cooler and