aFe 02-09 Chevrolet Trailblazer/ 02-09 GMC Envoy L6 4.2L Silver Bullet Throttle Body Spacer - SilveraFe 02 09 Chevrolet Trailblazer 02 09 GMC Envoy L6 4. 2L Silver Bullet Throttle Body Spacer Silver The serrated helix design creates air turbulence in the intake manifold. This turbulence increases the air pressure in the combustion chamber, resulting in increased performance and improved throttle response. The serrated helix combination design also reduces intake whistle that occurs with helix only designs (US PAT 07055513). This Silver Bullet