aFe Silver Bullet Throttle Body Spacers TBS Jeep Wrangler (TJ YJ) 91-06 4.0LSilver Bullet throttle body spacers create turbulence in the air flow at the point just prior entry into the engine increasing horsepower, torque and improving throttle response and fuel efficiency. Silver Bullet throttle body spacers are constructed out of durable T 6061 billet aluminum and using a unique serrated helix entry to create turbulence at the manifold while eliminating the annoying whistle found in other helix only throttle spacers.