just like everyone else is saying..you wont see any huge power gains from VF.. You may see better throttle response. But the same performance gains could be had from a $50 set of boyesen dual stage power reeds. You wont see the full potential of VF cages until you get into some bigger dune/drag type setups.
VF isn't always the best option..
problem is.. economy is so tuff right now.. that the market is being flooded with cheap bikes.. which lowers the value of everything.. Not to mention people dont have 10k sitting in a bank to buy with.. Banks will only lend what the blue book value is.. Thats why its better to part a bike then sell it outright.
biggest problem is mileage... you'll burn up A LOT more alky.. if I had to guess.. you'd burn through a full tank in about 10-20 min depending on the motor.