A good amount of noise comes from a two strokes intake believe it or not. Now that you have the exhaust sorted, you might try adding an air filter and see if that helps further. If the original was bulky or untenable, try one from one of the car guys suppliers. (You will have to re-tune the carb, but you will find it easier to tune, plus the engine/front of the plane will stay cleaner, and you will use less fuel.)

http://www.davesmotors.com/Products/AF-Air-Filters/

AV8TOR