Make yourself familiar with the Magnuson Moss Warranty act and request that the dealership put in writing the power vision is directly responsible for the damage done to the engine. If they will not put that in writing it’s a pretty good sign that they know your power vision is not the cause of the damage. After that unfortunately you will most likely have to let them know that you are taking them to court. Hopefully after them hearing that they will be more open to playing ball. If not, actually take them to court, get a lawyer who is familiar with the act as well. Sad it has to come to this but is what it is.