Small Block Intake

If it revs fine to 6200, then maybe you’re just expecting “more” out of it than there is.

The cam isn’t very big.
I wouldn’t expect to have to go higher than 54-5500 to use it all up.

Going back to the beginning of the thread....... I’d say if you can borrow a known good 750 from someone to try....... that would be a good test.