Martin, In your seminar at Perry you stated the temperature on the intake manifold while engine braking would slowly decrease. I agree if using an engine brake or compression brake, However if using an exhaust brake just the opposite is true. On my previous two coaches one a Cat and the other a Cummins (ISB) when using the exhaust brake the intake manifold temperature would increase and in some cases max out at 255 degrees. One time on the Grapevine the temperature stayed at 255 long enough for the dash "Check Engine Light" to come on. The light went out within a few seconds of disengaging the exhaust brake and the manifold temperature dropping off.