In my 250, I'd guess 110-115 before I backed off. It had Plenty of Power Left, I just didn't need to go that fast and started to run out of room.
I was leaving my Friend in the Smoke. He had never seen a tuned 6.4...So I showed him.
132mph in my Cadillac DeVille Concours.
Confirmed by GPS and Speedo. I think it would go more, but the message on the DTC said - Fuel Shutoff, Top Speed.
110mph on my HD Fatboy, then backed off. I really don't need to go that fast on it.