fuck new sprockets and expansion chambers, the first robs your top end and the second robs your low end. get a sweet lowend pipe for that bitch. Something with tons of backpressure. That's how my grande is set up and it will take 300 pounds up a steep hill like a champ and still go 30 on flats.
Or you could try to find a lowend expansion chamber. I would definitely recommend a performance variator. That will keep you revving higher.