no high engine brake

[Chamberpains]

20 psi is a bit high for 2nd stage jake. Mine won't peak passed 14 psi. I have a small CPL (8520) engine. I don't know if this makes the difference or what your 2nd stage being higher would mean. Im just stating that there is a difference.

When you cleaned the housing to the exhaust pressure sensor, did you ensure that no loose crumbs got blown back up to the sensor or reclogged anything.

Also having someone that knows what they're looking for with insite or calterm can make a world of difference. Maybe record a test drive using either one while monitoring all sensors. You more than likely have a slow j1708 diagnostic connection so you'll have to record a lengthy test drive on a pretty good hill. Both up and down it.