I think it sucked in some dirt through the exhaust system.....cause there are scratches on the bottom of the connecting rod and a small gouge in the piston......i always hade the air filter on there....the only way it could have gotten dirt in is becuase of the o.s. header, cause before i bought a some rubber things for the o.s. header to fit it wasnt making a seal.....so dirt must have gotten through there becuase i couldnt even shut the engine off with my finger on the exhaust, it would just keep running......

so im guessing that dirt got through the exhaust port then scrathced the bottom of the connecting rod and then it eventually made a litlle gouge on the piston.......not big enough for it to blow the engine but just enough for it to blow glow plugs and idle funny