M1 Intake Manifold SBM

Right! Big port up front is for the PVC.
The big one at the rear is for the power brake booster.
Do not share or splice the hose together. Always run them to each respective port.

The spacer is probably helping with HP. If you remove it, you may, MAY notice a power loss. I doubt it but it’s possible. Open spacers normally add top end power. At least on single planes with open plenums. Like the M1.