I had a diesel tech tell me that he thought it may be a injector return check valve that comes off the back of the CP3. He works on navistar motors for high lifts, so he is not familiar with the cummins set up. But he did say that it is a common problem that he runs across with those motors.

Anybody have any thoughts or have any problems with this part before?

Any thoughts would be greatly appreciated. I found it on Geno's.
http://www.genosgarage.com/CUMMINS-3.../#.VEU0VTJdWSo