There is a trick, but I really don't recommend it in your case since your idle and transition are so nice, and the trick is a bit difficult to do without screwing the carb up.

In your case, the numbers suggest you are making good power and you need more loading. What I recommend is going to a heavier prop load. If you would like more speed, go to an 18 x 8 prop. If you would like more static thrust, go to a 20 x 6 prop. In either case, I recommend switching to a Zoar prop. They are very good props, and also load the engine more than other props, which is what you want. You will think your engine sounds a bit lame, or less powerful, but just wait till you fly it; you'll be impressed. Do retune as normal for the new prop. Without taking the time to calculate it, I'm guessing that your prop tips are going supersonic at full throttle right now, which is both noisy and inefficient. (It does sound cool though, at least to me.) Anyway, expect the new combo to be more quiet, yet fly more powerfully, and probably help or solve that pesky burble. Most good setups prop for no more than 7500 on the ground, with many going for lower yet; like 6500. Personally, except for my highly souped up hot rods, which are a different story, I go for 7500 +/-.

AV8TOR