Vauxhall Astra ems stays on

The EMS Light came on and car lost power , had the problem diagnosed as swirl flaps and manifold both have been changed, as well having timing belt and water pump changed, the car is working fine and the power is not effected, when the car is plugged into the diagnostic comp it shows no fault code, the light is reset and comes back on within a mile or so. The car doesn't go into limp home mode and performs 100% , it's really stumping me the garage I bought the car from .........