The EGR system and the valve cover vent tubes leading into the intake manifold clogs stuff up REAL bad on these motors. I would say to delete the EGR and either get a catch can, or put breathers on the valve covers. This gums stuff up and aides in the carbon build up. I would try to run premium fuel with 2 cans of fuel injector cleaner--and RAG THE CRAP OUT OF THE MOTOR when having that in the tank. It will help clear up stuff in the cc.
Also very possible. And checking for this problem is VERY easy...

