Starts up and runs great but when I run at Full Throttle after a few minutes it will backfire and then lose a lot of speed have to run it at that speed for roughly 30 seconds and I can get it back up to full speed for roughly a minute or two then backfire again back to a little lower speed not having any luck on finding a way to correct it

 

Check the tank breather isn't blocked then check fuel flow from the tank. Difficult with the vacuum operated tap, but my guess is the fuel isn't flowing properly due to the tank filter blocked. Oddly enough I am cleaning out an Eiger tank today, (lots of water in it) but lots of paint flakes, grain and hay were stuck to the filter.

 

On my 02 Vinson there was a screen in the fuel inlet tube of the carb. I used a soft wire and some brake clean to clean it.