Mack MP8 engine brake

Does anyone know if Mack uses an exhaust brake or engine brake? From what I understand a lot of the newer engines are using exhaust brakes. Reason I'm asking is this truck just had the EGR cooler replaced which requires the turbo to be removed and now it screeches when the brake is on high and it's making around 25 lb of boost. No noise when it's under a full load pulling a hill at 40 lb of boost though. If these do use an exhaust brake I'm guessing a clamp isn't fully tightened and it's forcing air out somewhere but if it's an actual engine brake it could be something internal...this is a company truck I'm just trying to figure out how to write this up for repairs