Nick

Can't really help with the pipe question as I use a cannister, but I have a throttle curve on mine, makes a massive difference. These gas engines are not linear at all and by about 50% carb travel you are almost 75% throttle, so I have really 'softened' the lower end of mine travel to give me a more liner throttle response.

As a starter I run the engine and then adjust the throttle curve so that I get a drop in rpm per click of stick travel.