I think the dyno guy is responsible... Unless you had 100k + miles on your car, and even then you shouldnt have blown a rod, maybe a bearing but not a rod. The guy overloaded your car and snapped your rod 99.9% sure. I would talk with him and see if he will own up to any of the replacement cost, if not put him in touch with your attorney and contact the better buisness beareu, and the beareu of automotive repair...