Speedmaster vs Edelbrock air gap intakes

that 318 made 477 at enginemasters with a 247/247 cam and the crosswinds intake on it. Had ported 2.02 magnum R/T heads on it.
Ran mid 11’s in my 3400 pound car with a smaller cam in it than it had at enginemasters. Flat hood all steel bench seat Duster with my 320 behind the wheel
Guy i race with has your 408 in his Duster, been testing/ racing it for 2 seasons, car is setup to race pretty well. Best has been 11.90’s at 110 thus far. Should run way better than that.
Something is wrong with that 408! We got my brothers 67 barracuda to run 11.82 @114 without trying.