Overtake Phenolic Spacers 8mm ThickOvertake Phenolic Intake Manifold Thermal Spacer Reduce Heat, Increase Power Is your Subaru engine running at its full potential? One of the biggest obstacles to maximizing your engine's performance is heat soak when heat from your engine transfers into your intake manifold, reducing air density and limiting power. The cooler the intake air, the more horsepower your engine can achieve. That's where the Overtake Phenolic Intake Manifold Thermal Spacer