with the m4 can you get a drill bit and instructions, (its been awhile so memory is not good) get on the m4 site their tech support will know.... Dez as I remember has a m4... he'll see this and tell you for sure.....putting that exhaust on the bike I think is the most significant improvement you can make......
actually....my jetting is still stock
it runs ok enough, just a few pops on decel to tell me its too lean...if I ever quit having so much fun riding it, I'll mod it further