Got a 2012 LML Duramax with a white smoke issue. It's straight raw fuel. Truck starts great, will idle fine. It will intermittently run rough, but most of the time it runs smooth and just smokes. It will sometimes bump it's idle up to 1200 rpm and there is no way to bring it down. The truck is fully deleted, but stock otherwise. Drives fine down the highway, no smoke, and no surging or rough running. After you take it for a good drive it seems to be ok for a little while, but if you let it idle it goes right back to smoking. Any help at all will be greatly appreciated.