power valve size

With a roots blower, you are running off of the idle circuit around town at part throttle. Try leaning the mixture screws. Do you have 4 corner idling? Pull both carbs and square up the butterflies with the transition slots, then reset your idle speed and mixture. Not sure why you need 10.5 power valves, I run 6.5 in my two Demons. My vacuum at idle is 9 inches. I am on my 2nd set of plugs in 7 years and the pistons are still in it. Must be doing something right.