I'm not sure about that. I talked to a lot of guys that run Holley's that don't seem to have the same lean issue at the top of the gear. It may have something to do with the fuel inlet or the size of the bowl in relation to the float on a qjet not holding enough volume. Or it could be one of a hundred other things I suppose. It could be as simple as not having a return line( my car was originally a 350 car without the return). All I know is I've been chasing this problem for the last 4 motors. I think I got it licked now but I won't really know until I get it to the track or on the dyno for a varifyable test. No filter in the carb. Probably wouldn't hurt to replace the canister filter now that I think about it.
Yes, there are different sizing of fuel inlets. They can be enlarged easy enough with the right size drill bit.