Well, if you want to keep it simple; Open up the exhaust, take off the airbox lid and jet it up a bit.
You already have the DG, if you have the a/b lid on, your starving that engine for air.
Yeah yeah Powroll, Webcamshafts, Megacycle and it's about 450$ and then the cost of a piston and bore if needed - NOT CHEAP. It can run 650$ plus easy and it will still have the same stroke, just a slight overbore to clean it up.
Also, look at all the guys who have lately tossed in a 400EX carb; They've had issues in one or more portions of the power range. One guy even went back to a 350X carb.
None of this stuff is etched in stone, it's all trial and error. The bigger you build it, you will lose some reliability.
My "other" 350X is merely jetted up, has no airbox lid and a Supertrapp exhaust. It's a blast to ride and didn't kill my wallet................
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country