After having a sxi pro, a 750sxi, and a superjet I'll tell you right up front that the pro is the heaviest by far. If you want to freestyle this ski you should reinforce the hull. Beef up the underside of the handlepole mounting area, or it will crack down the sides.
The 750sx cylinder has better porting for low end. The fpp wet pipe is good with a higher compression head. The stock waterbox is ok. Boring the nozzle or getting a 750sx nozzle would help along with a pump cone. You can get an ignition advancer plate, too.
Get an aluminum handlepole. A shortened one. The stock steering gets sloppy, too. A superjet pole conversion would let you use a UMI steering kit, which would be a good solution.