The Yamaha has a really good woods motor. Hawk, (GNCC guy) says he prefers the FMF gnarly. (Although it didn't seem all that "magic" on my RM). I run a FMF Q, good power and I feel it is an important sound issue these days. V Force is good stuff, more power, crisper response, friendlier delivery. Leave your reed spacer in for smoother hit. More head-pipe length will make the motor "gruntier" too, (add 2-3 washers to exhaust port before pipe goes in). Or, does the Yamaha design let you do that? Don't know for sure. Have buddies that go from 6-12oz flywheel weights, just depends on your terrain. I think gearing is a terrain thing too, here in tight, rocky Missouri, adding 1-2 teeth to rear is usually the standard, for a "B" caliper rider, on an MX-converted bike. Enjoy!