isx cm871 overspooling

[Crash Dummy]

After all is said and done, ECM Programming had become corrupted, would not show faults of Turbo, no overspeed, or some other faults, dont ask me how, but this is what i was told. ECM off and Total Wipe, and reprogram. ECM then showed fault of ecm rpm at 150000 when engine was off,this after a test drive, as no faults were seen prior to removal. replaced speed sensor, same effect, different ecm showed same, so, we did some tracing of the harness, seems the speed sensor harness had broken. Replaced harness, and now speed sensor works correctly. My thoughts are someone wasn't paying enough attention when removing head for repairs and separated the harness wiring. We shall see, seems this isn't the first de-mandate performed by the shop I use, but has been the only one that developed the turbo destruction phase, so all were caught scratching heads.
It has been a very long ordeal, hopefully it all is fixed, as I stated before, after demandate, truck performed as it should have for a year, my thought is, if it had been a bad de mandate, I should have seen trouble long before a full year had passed, and the head gasket or turbo blowing much sooner.
Even the pre mandate engines would blow head gaskets, As I have had one i owned before do so, And when I wrenched in years previous. So, that said, A bad delete in my opinion should show its bad side much sooner than what I have experienced.
I do appreciate all the responses i have gotten from those here, and shall continue my pursuit of learning more of the way this engine does what it does here.