Holley/Demon Carb stumble

I suspect something is wrong with the metering blocks you ran with the demon/proform main body.
I run a Demon 750dp with 3 hole emulsion metering blocks. I tapped the holes and run .026 bleeds in all 3 with a .028 MAB This setup gives me a flat fuel curve all the way thru to WOT at sea level. Use the MAB to obtain a flat curve and jet to set AFR you want to run. If your blocks are stock the emulsion holes are .031. If you decide to tap, drill the .031 out to .052 and use a 6/32 tap to set the allen head brass set screws flush.
https://www.amazon.com/gp/product/B01N0KM570/?tag=fabo03-20
You also need to check the brass plugs on the top of the metering blocks. If they are leaking they are adding additional bleed air to the emulsion well and the carb will go leaner than you would expect. You can seal them with any good fuel resistant sealant.