I have a 91 SN. I'm pretty new, but I've seen this as a common concern about the Superjet, with lots of replies in the forums. It seems to be a tradeoff to having a more playful hull.
Most say you just need more tray time. That does seem to help, since I notice the problem a lot less now than I did last summer when I just started. You can also put an extended skid plate or shim the back of the plate slightly to push the nose down. I did not do either. A new intake grate supposedly helps - I went with the Worx 201 mostly since I wanted the pump to stay hooked up better but it did also help a little on the porpoising. It also seems like my ski porpoises more in glassy water than it does in choppy water. I let an experienced rider take if for a spin last weekend to hear what he thought of the ride, and after a few seconds getting used to it he was able to blast around at full throttle and was quite happy with the ride. So, I'm not sure how much experience you already have, but tray time may be the best solution.