I jettted my '98 with a "Factory" kit - kit had me drill the slides (no big deal), change main jets and change slide springs - all pretty easy except for getting the carbs off the manifold. We never did succeed in doing that, so we ended up doing the jets with the carbs still on the bike - possible, but many banged knuckles!!
Anyway, the jet kit was wonderful. Completely eliminated the flat spot at about 5500 RPM, smoothed out the power band across the entire RPM range, and did not seem to have an adverse effect on mileage. In fact, I just had to have the bike smog checked, and it passed with flying colors.
Just thought you should know
-Jim