Energy Suspension polyurethane bushings go a long way to preventing unwanted drivetrain movement on street and track cars alike. We recommend them for all Miata builds, but they are required when running our Miata front differential mount with the PPF deleted. You'll notice a slight increase in driveline noise with these bushings, but not much. 

For a complete Miata differential upgrade, also install our Differential Am Reinforcement Plates when replacing the bushings.