Superjet Upgrade Help

Just bought a stock 2001 SJ and seem to notice a sound almost like loose marbles as I ride. Ski run fine and is quite out of the water.Not really that bad but wanted to see if anyone has had a simialr experience?

I ride river and ocean and am looking for recommendations on a ride plate,intake grate and impeller that work well all around?

Any thoughts are appreciated.

Thanks --- Michael