Get it dialed in and running strong. Even a stock XS tuned right should pull 2 with no problem. If it is not enough power for you and the only mods are to pull 2 then maybe you need a second bike for that purpose. Stay with stock timing. Check compression, timing chain adjust and valve clearances. Proper ignition, even stock must be in good condition. Carbs can be more then the it appears, especially if you are at altitude. Air filters and exhaust complete the fuel system tuning.
If you change the rear sprocket you will probbaly need a longer chain. Not sure how much adjustment will allow for? Be sure to use the old "one change at a time" so you can keep track of what made a difference, good or bad.