I can say that there is no backflow pulse through the carburetor like on a 2-stroke. The only problem is that the Bernoulli effect from the propwash acting on the open inlet of the carburetor is effectively reducing the air pressure there. The engine gains about 1,000 rpm when I put my hand in front of the carb inlet at WOT. I think from everybody's comments I'm going to bag the velocity stack idea for now and put the air cleaner back on. Thanks for the input.

Charlie