MACE PERFORMANCE LOWER MANIFOLD INSULATOR TO SUIT NISSAN SKYLINE R31 RB30E 3.0L I6Exclusive to Mace Engineering, here we have our design registered lower manifold insulators to suit the Nissan R31 Skyline fitted with an RB30 3. 0L 6 cylinder engine. What are manifold insulators and what do they do? Manifold insulatorsare 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,