Once again, try these two things before you go hog wild.
1. Install an aftermarket Aquavein intake grate.
2. Stuff the pump shoe housing with a pump shoe housing stuff kit.
You can do these two things yourself, and you will need the grate, the kit and some 3M sealer. I did this to my 2001 XLT 1200 which was exhibiting the same characteristics that you describe, and the problem was rectified. A heck of a lot easier than messing with the impeller.
I, of course, eventually changed the impeller but that had more to do with speed than with cavitation. costs were about $100 for the intake grate, $80 for the shoe stuffing and $15 for the 3M marine sealer.
Give it a try before you mess with the impeller. It may save you a lot of time and headache.