Best exhaust Fat Boy 4 avail at Duncanracing.com for 699.00 thing is this is what team green use on there factory backed race machine's and atv connection forum member Greenteam who race's the V for Kawasaki swear's by them.
Best intake either home made snorkel or Diamond G carbon fiber snorkel for 139.95 see bearman's post several below this one.
Best front bumper I like the AC racing stadium bumper seen lot's of people using this bumper while racing.
Best rear bar I would reccomend a 6 pack rack from either ac or prm or a cargo rack from prm because if your going to do some aggresive trail riding for any extended period of time you will need to bring gas with you beleave me these thing's are gas hog's.
Other mod's to do
Ims 4.6 gal gas tank
Trailtech handle bar's,enduro comp,and dash
I put motion pro twist throttle on mine I hated that stiff a$$ thumb throttle
Web cam's make a cam kit for it
Also 4 stroke tech make's a 785cc kit for it
Diamond G is working on a performance cdi for it
Vortex ignition's is working on a programable cdi for it
You could build a turbo kit for it
with fuel injection completly programable of course!
sorry got a little carried away with the mod's there
Note some people do not reccomend making hole's in the air box because the carb's are vacuum operated.