My Evo .46 surged also. Adjusted needles, changed plugs, tried everything.

Found a leak in the fuel tank at the stopper. Fixed leak; problem solved.

You don't have to pull the tank to check for leak. Pull the lines off the carb & muffler nipple, plug the carb line & suck on the pressure line. After 5 or 6 sucks, stick the end of your tongue in the line to block it. You should feel a vacuum trying to pull your tongue into the line. If not; you got a leak.

Shack