Wick500,
I don't understand why you can't open the 500 forums, sometimes I can't get logged on to the site, however when I do it is all open.
There are no restrictions or anything..
You could start with the carb, make sure everything is cleaned up and working properly.
Cables,Slide, fuel inlet needle is not boogered and moves freely.
I know what it's like to have STC (Stuck Throttle Condition).
Like GDubb says, the float level,plugged vent lines, will run the carb bowl empty (after that WOT run) and the engine will go into a lean run away condition.
I have also seen fuel petcocks get plugged and restrict the fuel.
Check that out and let us know what you find and we'll go from there.
Tuck\o/