Hello. My name is Mark and I will be assisting you today.
I would suggest you check the car for a misfire, possibly a faulty coil pack and for a blocked catalytic converter.
That is a possibility but I don't think it would cause a noise from the exhaust.
I would try my first suggestions of misfire and blocked catalyst.
Why haven't you mentioned the light staying on all the time before now?
Also, if the light is on it means there must be a fault code stored. Can you tell me this code(s).
I would have thought so but if not you should call the garage and aske them for it.