643 HP at the wheels, then......

things were going so well on the dyno when the water meth decided to fault. we were about to do a graphed pull when this happened. shut here down right away and thought things were all good. on restart smoke started spewing from the breathers and, well the rest is history. we were at 643 hp at the wheels 17 psi boost.
stripped down motor yesterday. #8 piston f#@ked, head gasket exploded into valley. detonation the cause. **** happens ah.
pistons are forged Mahle.