Although I never received any replies on my post, I thought I would give an update for anyone having the same issues.
I have slowly started breaking down my ski and have now completely removed the engine. I am a shade tree mechanic, but it has actually been pretty straightforward using the Service Manual. For the 2004 XLT 800, you can remove the Cylinder Head without removing the engine, but that is as far as you can go. In order to really examine everything, you must remove the Exhaust Manifold which requires the removel of the engine. Although it was a little heavy, I was able to remove it by myself with no other assistance or engine lift. If there were 2 adults then it would be a breeze. Once you remove the engine then you can access the 2 YPVS's and the actual Cylinders so you can see the Pistons.
Both of my pistons looked great; however, I found the problem was one of the Valves from the YPVS had broken in half. It just so happened that it corresponded with the cylinder that had a Compression reading of 150 psi. The broken valve prevented it from rotating back and forth into the cylinder which was the cause for the loss of power, or at least I hope.
If I encounter anything else I will update as needed. Hope this helps someone else.