I just finished putting a new White Bros. E-series exhaust, ProDesign Proflow air filter kit and Dial-a-Jet system on my wife's 400 stocker and now she really jumps.
It was amazing how responsive the throttle is now because of the improvements. I put the Dial-a-Jet kit on our bikes with a little bit of nervousness but because we live at 6500' and we also like ride at sea level it seemed worth it than to deal with the whole jetting issues on a constant basis or always be robbed of precious horsepower.
It was definitely worth it![img]i/expressions/face-icon-small-happy.gif[/img]