Dzenno went Through similar issues and found out it was this: hope this is not your case but look at the other forums to find his post on it
Camshaft rectangrings and cam bearing ledges were broken/worn.
It can possibly be another issue as you stated it did this also in stock. Dzenno issue happens at high rpm which boost is greater than 13psi.
Last edited by cn555ic; 09-23-2012 at 10:13 AM.