Re: Advance. Do try to confirm that the centrifugal advance is correct; it can have a significant effect on throttle response.

Re: WUR. Unplug the WUR heater connection from cold. Eventually block heat will raise the WUR temperature, however, the delay will enable you to tell if the WUR is the culprit.

At the risk of stating the obvious, do check that the spark plug wires are in the correct firing order.