OK... I go way back in PWC... and I've had a bunch of "Mod'ed" skis over the years... but for where you ride... and the way you ride... keep it stock. Engine mods normally take away from reliability.
As far as nozzles.... If you put on a smaller nozzle, you will increase the pressure, and velocity (assuming your pump is good) and in turn, giving the ski a higher top speed. The down side to this is... you will loose "Out of the hole" performance... and if you go past the sweet spot... you will bog the engine, and loose performance every where. Generally, if you are going to play with nozzle size... you need a bunch of sizes, and you tune the ski for the conditions.
With that said... a bigger nozzle will give you better acceleration, but will drop your top speed.
If I was you... I would put in a top loader intake grate, and a Skat-Track swirl impeller, and call it a day.
If you really need to go faster.... buy a ski with a larger engine. (It's cheaper in the long run) You can drop $3K~$4k on your ski, and only gain 5 to 10 MPH, and not be as reliable as a ski with a large engine.
Just my 2 cents.... take it for what it's worth.
With all that said.... I'm thinking of putting a 900 engine in my little Si. :cheers:
