I had this unit in the shop for a low power condition. Operator stated that the truck would not go over 35 MPH. Upon inspection I found an EGR code. I pulled the EGR and in the process broke the the actuator off from the valve portion. After removing the EGR in chunks I found the EGR circuit all coked up and wet. I ran the bore scope down the EGR crossover tube and found white spots. I started thinking EGR cooler as usual. I've got the cooler off and decided to change the exhaust manifold gasket while I had it apart. After removing the exhaust manifold I found Cylinders 2 & 3 were very clean compared to the rest of the ports. They had coolant stains in the port. I was wondering if anyone else has seen this condition? Are these heads prone to cracking?