I removed the plenum this weekend and replaced the spark plugs. I noticed the plenum was filthy dirty internally. I mean that where the gasket attaches to the plenum, there is a group of 6 flapps that open and closed. The flaps had so much gunk on them that the flaps could not close all the way. I could not figure out what the flap valving system was there for. I cleaned it the best I could and scrapped the gunk off the plastic valves. It looked like the only way it could get sludge into the plenum was thru the EGR valve line. Does that make sense? Also, besides running the plenum thru a parts washer, are there engine additives that could be added to the oil/fuel to help eliminate and cleanup the gunk? Thanks!

 

The flaps you are referring to are a part of the variable length intake Chrysler came up with. They open and close based on driving conditions to optimize performance.

The sludge is oil most likely sucked up through the PCV system. There is a way to put a catch can on the line and will stop most of the oil from getting in the intake. Burning oil also decreases performance.