How is the oil coming into the intake from the valve covers? Is there a noticeable leak from the plenum to the intake manifold? My egr was filthy when I first removed it, all oily and carbonated. I think this is fairly normal and should just be cleaned up. You could take the plenum down and have it cleaned out at a machine shop, or do it yourself, maybe even take off the intake manifold and have it cleaned as well. Put it back together in like new condition will probably give you a smoother idle and acceleration. I did not put mine back in clean at first and it still ran fine, could have been better though.