The center carb. came with Holley #63 jets in it, the 4382 outboard carb should have a Holley part # 34r-6153-34 metering plate in it and it should have had a .052 fuel inlet size in the bottom of that metering plate, the other carb # 4383 should have had a r34-8153-35 plate number in it with a .071 fuel inlet size hole on the bottom of it.
I have heard a lot of people on here say that drilling those holes out to.086 works good
My set of original six pack 1970 carbs like #63 jets in the center carb and .096 air bleed jets in the one side and .092 size air bleeds in the other. Those plates had the original holes plug off and where drilled out and tap to use Holley screw in air bleeds. that set up worked real well Once I got the fuel system straighten out with the proper size pre fuel pump fuel filter size it didn't want any richer jetting than it had
I did try richening up the out board carbs jet sizes by .004 and it slowed down, I didn't try leaning it down though
All the stock six pack center carbs I worked on didn't like a lot more jet size in them, maybe one or two sizes up or down, no more than that though
Take a look at your outboard carbs. metering plate numbers, both of them and post it on here to see if they are stock or been change like the center carb jets have been
Make sure that the fuel feed holes(channels) for the power valve haven't been plug off also
Let us know what you find