Look through the forum on rejetting. I don't know the jet sizes per year I just know the more recent years have leaner jets. I used a stage 1 kit from 6 sigma. I told them my elevation and year and they sent a few jet options.

You can go ahead and do the muffler first and see how it runs. It will not hurt it to ride without rejetting. So if it's riding great, then leave it alone.