I don't have an exhaust brake on my '06 truck, but we just got word from Delphi today that the POD is available for replacement so you won't have to replace the entire unit. They even provide instructions to check out the drive unit so that you can tell if it is good or bad. The POD is less than $100! PM me or email me and I'll let you know about the information I got! Hope it will help.
Here's the instructions for checking out the drive unit:
Before fitting a new Vacuum Pod:
• Confirm the frame is in good condition.
• Check to see if the drive can be rotated easily (without the Pod installed) and is free of dirt
and contamination.
• Check the condition of the Pod push rod. A worn push rod could indicate a damaged cam.
Visually inspect the cam lobe.
• Check the lubrication level in the frame. It should contain approximately 8-12 cubic centimeters of 80-90W gear lube.
• Install the new Pod with the 4 bolts previously removed during inspection. Torque the bolts to 10-14 NM and reinstall assembly to vehicle.