I see now. Your Pac Brake is quite similar to the Blue Ox I have on my 7.3. Just a controlled shutter that shuts off the exhaust and creates back pressure in the engine.
Kind of surprised being a DDEC motor it didn't come with mechanical (under the valve cover retarders). Shutter type retarders are never used on commercial trucks, always mechanical retarders.
I rarely use mine but I have it anyway. A 4 stroke diesel is a fantastic compressr when you hold the exhaust valve slightly open during braking. The advantage to an external retarder is it's simple and requires no adjustment. The downside is, it's nowhere as efficient as a mechanical retarder acting on the exhaust valves.
So now you are collecting turbo's? Might want to go compound turbocharging....lol