The L9 hack does indeed prevent the DFM from enabling but it absolutely does not prevent the lifters from moving and eventually failing.
I drove mine that way and it lead me right into a new motor at 16K for the same issue the OP has.
Well I finally got the truck back. #5 Rod bearing ate itself and jacked up the crank journal. Metal shavings all the way up in the top of the heads. Replaced motor, oil cooler, radiator and all oil cooler lines.
Update....got a call from the dealership today that the motor came in, now god only knows how long its going to take the parts changers to do a motor swap
I did the same in my AT4 before the ZR2 until a really smart mechanical engineer showed/explained to me that the lifters still move whether AFM/DFM is active or not so leaving in L9 doesn't prolong life of them.