engine brake stuck on?

[sbtrucking]

Hello fellas,
I have a problem with my cm2250 it ran great for past couple hundred miles with mm tune, I was driving the other day it developed a problem it started loosing power and slowing down fast, it was pinging and smoking a lot, I stopped and changed the filters I thought they pluged up because I shocked the tanks with biocide. I thought problem was fixed with filter change truck ran great until I decided to test the engine brake, same thing happend like I dropped an anchor lots of smoke and feels like pinging crawling at few mph, I turn the engine brake off after a minute it clears drives good again, everytime I engage the engine brake same thing, seems loke its getting stuck on. what can couse it?
thanks in advance for any help