So, I had my head gaskets replaced by a shop. I have noticed a knocking or a ticking sound from the engine around 1700-2000 rpm. It is not noticeable at the other rpm ranges. It definitely gets louder when I am working the engine hard towing in those rpms. I have owned this truck since it was new and I know it didn’t make this sound before the head gasket job. It sounds like it is on the driver’s side and it is rpm related and seems like it is just one cylinder. This was a highly recommended shop that is known for duramax head gasket jobs. Any thoughts on what might be causing this noise?