OK guys i need some help here. i tunned a friends 05' lly, i put in Pat's 20/20 tow tune. he only wanted a little more power and better mileage. the truck was fairly neglected, when they changed his trans oil it came out black , and the guy doesn't really keep up on maintenance. now one of his head gaskets is blown. what I'm really looking for is a little reassurance that my tune didn't cause this and it is a common problem on lly's. also he wants to know about how much it would cost him to replace them? thanks for the input.