Your compression sounds low. Might have cooked your rings. What RPM are you getting to? Does it ever backfire on you? If so, that's a lean-condition indicator. If you're running full rpm and getting a lot of cavitation at take-off, you might have a bad wear ring, or impeller (or both). Have you inspected your rave valves? If those aren't opening, you'll have shit performance up top. Your engine will "wake up" when those things open up. Should occur around 5k rpm. Have you checked your fuel/water separator? If you have a bunch of water in there, it'll run like ass. There are so many potential reasons why a 2-stroke can run poorly... need more info.