aFe Silver Bullet Throttle Body Spacer 07-13 BMW 328i (E90/E91/E92/E93) L6-3.0L N52aFe Silver Bullet Throttle Body Spacer 07 13 BMW 328i (E90 E91 E92 E93) L6 3. 0L N52 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