2003 Peterbilt 565 ISX. How do I drive this thing?

I know this was posted a few months ago but was wondering if you found the problem yet? I had a similar problem with the engine brake although mine would make the truck feel like it was bouncing when you hit the engine brake. Replaced the engine brake wiring harness, both solenoids and had the overhead ran. Cured it a little but not completely. Ended up needing new rocker arms on the engine brake side. Found they were just out of specs but was still able to run overhead. Replaced rocker arms ($316 a piece x 6) re-ran overhead and now she brakes like she did when she was brand new.