True! Not enough plenum is one.
A really big engine with not enough intake.
This is where a MP/TR or the Indy intake comes in rather handy. There very good for big engines.
Below are some pictures of the MP/TR and the Edelbrock STR (Street Tunnel Ram) and there plenum differences.
Both are a hell of an intake when used in there respective parameters.
If, IF! I was to use one of these below on your engine, it would be the Edelbrock STR.
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