If you machine the jug correctly you'll have high compression which is where you get real power. You'll need an oil cooler for the heat to run 91 octane and a Barnett Clutch for the added power if you do it right. My clutch started slipping in 3rd and 5th immediately and it's essentially a brand new bike. Do not run a big bore with high compression lean, it gets hot really fast.
The stock carb tunes easily. There's a better carb for more power but nothing is as easy to tune as the stock carb. I use a gs500 filter element in the stock airbox.