Its gotta breathe & it needs a proper fuel mix thru the RPM range. Supertrapp exhaust is tunable. Jetting the carb is the least step forward, Lancer sells an upgrade carb. The cam isnt what it could be. Lancer has 2 levels of better performance. If you lighten it up, you go a lot quicker. If youre fat, lose some weight! Youll smile when you look in the mirror AND when you twist the grip.
The intake can be worked over a bit & since it is a suction type event, & exhaust has a piston shoving it, I kinda think there is some gain to be made there. I modded the intake & increased the volume of the airbox, so the volume between the carb & air filter was greater.
Cleaning up the exhaust port is a good idea, as it is pretty restrictive.
The header has a small inner pipe. If you have one made thats open, then youve gained. I cut mine up & pulled the inner pipe & had it welded back together. The welder was so taken by it, he did it for free.
Old Feller has an air filter mod that I would have done had I not already paid the $$$ for the K&N.
If you want more Grunt or more top end, you can go to a chain drive.
Others will expand on this, as Im sure theres no way Ive covered all the bases.
Best of luck in finding the ride you want.