I have a customer who's been chasing a fault where intermittantly the timing goes massivly retarded, into the negatives, we have replaced cam/crank sensors, I have done a relearn with a Snap On scan tool and the cam error is 0, when not faulting the car runs very well, it has a cam and heads in it. The LS1 ecu is using a van calibtation. I don't know if I've missed something in the tune, we don't get many of these in Aus, it seems to happen from startup intermittantly and sometimes a start stop will rectify it.
I've attached the tune and am open to any suggestions.