can anyone shed any light on this problem please, got a y reg hyundai coupe for the past few weeks its been under reving as if there is no power to it and then it will over rv as though theres to much power to it its going in the garage tommorow for the 3rd time at first they cleaned the throttle and a valve that didnt work then they said there was a loose wire on the throttle that hasnt worked so now they saying it could be a valve that wants replacing io valve or something like that does anyone know about these cars and possible symton answers much appreciated thanks