Intake manifold. Copied Elddebrock performer RPM.
About eight years ago I purchased a crosswind manifold for my 410 stroker that had a weihand manifold on it and it ran like crap . Possibly sucking air maybe in the valley. I have fitted numerous manifolds over the years and never had any issues, but I think this one wasn't machined correctly. I paid $300 Australian for it but I just went and bought a edelbrock air gap for it at over $650 Aud and never had a problem with that. I sold the crosswind at a swap meet for $100 and the guy thought he got a bargain. Edelbrock manifolds are around $1000 AU now so are very expensive for us aussies!