You won't find an Edelbrock Performer RPM Air Gap manifold like this one on the shelf. Marvin pulls these rascals out of the box from Summit Racing and massages them to MCE standards. He works the passages and does a port match, then he works the plenum area to improve airflow and reduce turbulence. A 1/2-inch phenolic carburetor spacer improves torque and keeps the heat farther away from the carburetor. Note the absence of rough edges in the plenum, which results in less turbulence and air disruption.