The most basic things are often over looked, and they dramatically affect how your bike performs.
-Engine condition
-Jetting
-Suspension setup & condition
-Lubrication and condition of all moving parts (linkage, swingarm, cables, etc.)
-Condition of brakes & fluid
Make sure those 5 things are working how they should, and you will be just as competitive on your '98 as you would be on a new '05.
Assuming you have the powervalve cleaned and working properly.
Try different settings with the powervalve preload spring.
A mag once printed to take a little preload off...
but that made my '00 fall flat on it's face.
I wound up with about 1/8 of a turn extra preload and it made a big difference.