engine brake issue

Could be the EPG or it could be an EGR valve stuck open. The EPG will kick in at a lesser that brakeing air pressure to engage it's warmhold to help the engine heat up or maintain heat. If an EGR valve is stuck open, when the EPG engages, exhaust back pressure rises and an overwhelming amount of egr is pressed into the engine. When this occurs, the engine reacts by choking down to almost stall and the epg releases. The engine runs ok for a few seconds and then the issue repeats when it re-engages.