Bad EGR cooler?

[cantrucker]

so here's the update I did pull off the EGR cooler and clean it very well but not much carbon came off, I also verified that its the cummins original cooler so not an aftermarket part issue. The egr cooler was also pressure tested and no leaks. I also changed the ebp sensor while at it, So all egr sensors are new and the egr has been cleaned out.

But the truck is still sluggish and seems like its derated and there is black smoke on hard pulls or hills. So what could it be should I check the injectors next? overhead? bad egr temp sensor?

Any help would be appreciated, Thanks.