If someone had asked long before now about getting ten more HP that was halfway civil as you are now, we would have told you how to get it. The dyno sheet posted with 10 more HP was on gasoline, the engine needs to have an air/fuel ratio between 13.2 and 13.7, the engine load must be the same at peak horsepower on both pipes, the Snipers need a 2 teeth smaller sprocket on the rear to make them mph the same as Shearer because they peak at an earlier rpm. When put on an a engine that makes .24 or more hp per cc on gas, you will see your 10 hp.
The margin of hp gain on a cast engine (.2 hp per cc) is very small, as the engine becomes more efficient, the split between the two pipes will be more obvious. Snipers are tuned to 200 BMEP at the crank and 716 Celsius during blowdown.