What in either of your posts says you don't have a C Brake? Maybe you should elaborate?! Or are you having fun being a waste of posts? By the bottom of your post, called a sig if you want to talk like you know something, both of you have MY DP's that would have C Brakes with the ISL's you both identified.
Cummins implemented the C brake on the ISL 375/400 around 2002-2003 which means you should have it. It is still a 2 stage Jake brake with added retarding power that comes from building boost to aid the compression release side... makes sense as your seeing boost while braking (thou you seem unwilling to determine if you have boost while not braking).
If you have both have an older enigine that your MY DP then you may have a traditional compression release brake, but it will NOT be the source of your boost while braking.
Stop being argumentative and answer some questions and provide some info, or go away as your not really being helpful just wasting space.
You foul one step further an post your ESN and I'll use my Cummins account to get all the data needed.
