BBK 86-95 Mustang 5.0 Phenolic Manifold Spacer Kit TFS Track Street Heat 3/8BBK Performance phenolic intake manifold spacer kits have proven to be a great way to increase performance for late model Ford EFI owners. Each Phenolic spacer is CNC Machined from 3 8 inch phenolic material, these manifold spacer kits increase power by reducing the transfer of heat from the lower manifold to upper air intake manifold. This produces lower air intake temperatures which results in added horsepower and the ability to add more timing