1998 STX 1100 cavitating help needed

Hello all - I have a 1998 STX 1100 hoping to get a little help with. Last year, it ran great all summer but right at end of season, heard a rattling noise from the pump. It went away and thought nothing of it. That was the last day we had it out last year then winterized it correctly. First time in this season, it started well and hit 7500 rpms like normal but did not get the same speed.....maybe 40 when last year, we were seeing 56. The most noticable difference was in the corners.....seems to be cavitating really bad. Still getting high RPMs but just not pushing water like it should. Seems to cavitate really bad. I know this all sounds like a jet/impeller issue but I cannot see or feel any damage to the impeller or housing. I initially thought the sound I heard last year was a spun bearing but then it went away ........so maybe debri in jet. I got the impeller socket and will pull the jet out but just hard to believe I am having such a big difference in performance without any physical damage. My questions are....1)how do I check for proper clearence between impeller and housing? 2) If I find excessive clearance between housing and impeller, has anyone ever used JB Weld then sand smooth to reduce the diameter? 3) If I have to replace the impeller for some reason, is stainless worth the extra cost? Thanks for your help