The serrated/helix design (US PAT 07055513) creates turbulence in the intake manifold and increases air pressure in the combustion chamber for better performance. This unique entry design also reduces intake whistle that commonly occurs with other helix-only styles. The addition of a Silver Bullet throttle body spacer lengthens the intake tract, which increases air intake speed, resulting in improved throttle response and overall performance. All Silver Bullet throttle body spacers are precision machined from 6061-T6 billet aluminum for lightweight, high strength, and a black anodized finish. This Silver Bullet throttle body spacer includes quality, machined screws, allowing for a secure, factory-like, non-damaging install to your factory intake manifold. This throttle body spacer will fit aFe Power intakes P/N: 51-81012-B, 54-81012-B, 51-81012-C, 54-81012-C, 54-13053D and 54-13053R. Silver Bullet Throttle Body Spacer Kit BMW 328i (E90/91/93) 07-13 L6-3.0L N52 BMW 328i (E90/91/93) 07-13 L6-3.0L N52