I experienced similar hard shifts and some sluggishness...I ended up doing just what Jeremy indicated...checked and adjusted the vacuum as well as some miner adjustment to the Bowden cable (search that one) Be a bit patient -- I've learned this is an art and becomes a balancing act. Suggest you go back to original vacuum setup. There's plenty of threads on this site, including diagrams of the system.

My sluggishness was caused by a dirty fuel filter -- simple fix Have you checked that. Unlike gassers, I've found I can't ignore the fuel filter.

My hard shifts went away by adjusting the vacuum down to 9-10 Hg. (0 at full throttle) and chaging the shift points slightly w/the Bowden cable. Discovered by some trial & error. (use small adjustments & then drive it)

Good luck...this forum is incredible, so you'll find nearly any scenario here.