Youll probably find it has nothing to do with airflow through the intake.
I think itll be caused by normal engine vibrations which do resonate with the intake at certain RPMs.
Itll be different to the old intake as its different size, weight, mounting, etc will tune it for different frequencies.
Not much you can do really other than braceing it to the engine better.
Mybe run a couple of braces from the underside of the manifold down to the engine mount?
Not a nice way to do it, but itll really firm up the intake and stop the problem... itll also help to reduce fatigue on those alloy welds in the future.
Bookmarks