I was wondering how much the average cost of replacing a camshaft in a 2007 Mustang 4.0. I had the check engine light come on and the car starting to drive very poorly. I have a code reader and it came up as p0340 and p0340 p. All I need to know is how much the average cost will be. I am also having another problem where my exhaust is smelling like sulfur. I think it is the cats but I am not sure.