My turn to ask for help with a Holley.

Superformance gaskets are far and away the best.

Make sure the main body is flat. If it's billet it probably is. If it's cast, it probably isn't.

Also, screw the power valve into the metering block and put the metering block on the main body and make damn sure the power valve isn't hitting the boss in the main body. 90% of the cast main bodies hit the power valve, especially with the tick power valve gaskets they use now. I've only seen one billet main body have that issue but I check them all.

Also, set your power valve opening based on cruise vacuum and NOT on idle vacuum.