As a former M109 owner, I know they have lots of power and are fun to ride. They do well in the turns, but you have to adjust your feet. My boot heels would touch before the pegs, and actually pulled a foot off the peg in a quick S turn. Ouch!
Also, second gear is crap. Anyone who rides hard will have a problem with it giving out.
The power they give you, is all you can reliably get. Intake and exhaust with a PC is ok, but the lower cases won't hold up to any more. A few guys that got head work for an extra 20 hp never got over 20K miles before the knocking started.