Can the throttle be changed from country five to country six?

You can't. The emission standard of National VI is stricter than that of National V, which involves many technical improvements, including engine combustion system, numerical control system, fuel system, tail gas aftertreatment equipment and so on. It is very important to coordinate and match these systems and components. Only replacing the throttle valve can not meet the requirements of the national six emission standards for the whole system, so the purpose of emission upgrading can not be achieved.