wtf would cause this to happen???

[kouki_drifter]

ok so i took my 97 kouki with an s14 sr20det that i rebuilt to tune and for one the new t2871rs t04s housing .86 exhaust turbo was only boosting 16.5lbs of boost with my tru boost set to 80% so i made 393hp 364ftlbs of torque to the wheels. I drove the car about 15miles after the tune it was running beast, i tuned out of town so I loaded it up on the trailer and brought it the 100mi trip home I unloaded it let it warm up for about 10mins drove down the road, opened it up in first to the redline let off and stopped about 1/16 of a mile down the road at a buddies house. He wasnt home so I reversed out of the drive way, as i reversed there was a white cloud of smoke that came out of the exhaust and covered the whole car so i drove it forward and turned it off, tried to start it again and it stopped got stuck pulled it home pulled the head the next day and this is what i found