Ok then if the choke kills it instantly the carbs are only starved of fuel at speed.
What would starve the carbs of fuel or air? Pinched vent hoses, the tank not venting, stopped up air filter, bad fuel pump, stopped up fuel line, stopped up carb jets.
Open the gas caps and ride it with them open. If it still does it then its not a vent issue. It has to be either poor fuel delivery OR too much air screwing up the ratio ala carb boot loose.