Quote: OOPS! RIGHT, NO AIR GAP for 400s. You'll have to block the exhaust crossover to get max benefits but still a great manifold. Air gaps and regular Perf RPMs have AFAIK the same interior configuration as far as ports and plenum. R.
I thought the RPM air gap for the 383 would fit w/o any modifications. How do I block off the exhaust crossover?
