https://www.dieselhub.com/specs/6.6l-l8t.html
I don’t feel that I lost any low end torque. The curve on the diesel hub if true shows over 300 ft/lbs with the 6.6 L8T around 1200 rpms. The truck runs good. I would say a modest bump is a good way to explain it. A 5.3 will never get those numbers...