A Detroit 500 engine riddle, can it be solved

My friend owns a 1999 Peterbilt with a series 60 Detroit 500. Last week, the truck kept cutting off, and he was in Salina, Ks and took it by a Detroit dealership. They told him that some wires were loose going to the ecm, tightened them up, and also some wires that go to the accelerator pedal needed repair. After the repair work, the truck started running fine again. They also got his cruise control back working, as it had been inoperable.

Today, the truck was in mississippi and the turbo went out. This turbo is not even a year old, a Borg Warner aftermarket. According to the shop he bought it from, BW had issues with seals in certain models and the mechanic said the seals were bad in this one. So, they put the new turbo on, check the connections, and fire the truck up. The truck idles fine for about five or six minutes, so they bump up the idle with the cruise control. All of the sudden, the engine starts accelerating wide open, and it will not cut off.

The driver cut the cruise off, and the truck continued to run wide open. He also turned the key off, but it still continued to run wide open. He and the mechanic got scared waiting for it to throw a rod, and they ran out of the shop. The shop has at least a 20 foot roof in it, and when the engine finally gave he said it shot water and oil everywhere, insomuch that water hit the ceiling in the shop.

I assume that the motor is blown, probably a cracked head, etc. The question is what could the dealership have wired back incorrectly that would make the truck run wide open that even when shut off it kept on running wide open? The truck is governed, but supposedly it ran past the rpm governor. This is all secondhand information as I was not there. Any ideas? Thanks in advance.

Shogun

 

So far it has puzzled some mechanics. I am assuming it is something to do with the wiring, since a simple turbo swap would have no effect on the motor running wild. Its anyone's guess right now.

 

Really Stranger? Could it be that the blown turbo also allowed oil into the intake side? The mechanic said that the seal on the slightly used turbo was bad.