Engines too lean on the high side. Don't listen to them, they want to screw you out of your money. There's no doubt the 3.3 has more power it's a bigger cc engine, but as far as your engine goes, it's more than likly running to lean on the high side back the high side needle out about a 1/16th to an 1/8th of a turn. also just to be sure, check your fuel line where it runs near that gear on the top of that over geared volcano transmission to see if it has any rubbing where it may have rubbed on the spur gear. If there's a hole in it that will also cause a lean condtion, thus the cutting out. You can also check that the fuel tank lid is holding pressure by plugging one end of one of the fuel lines and gently blowing in the other fuel line and see if it holds pressure or if it's easy to blow into and it doesn't hold pressure, this will also cause a lean condition. Let me know how this works out. Oh by the way, the Trx3.3 or 3.3R will destroy your drive train, mostly the diff gears.