Hello again wonderful and willing Bitogers! Sitting here enjoying a Samuel Adams Boston Larger after an exciting time working on "Thunder the Wonder Pig." She's been running poor of late and I thought perhaps a new EGR valve might in order. Sure enough, pulled the old valve and was amazed at the amount of gunk and carbon underneath. What caused me to stop and ponder was the kind of material beneath the EGR valve. The top layer was brown in color - like old, dried tea leaves. This was powdery and was easy to clean. Under the brown powder was a layer of hard black carbon which I chipped free with a small screw driver. Beneath that was a layer of black goo/gunk. It had the consistency of tar and was very hard to clean. Why these different "layers"? As Martin Luther would say in his catechetical way: "What does this mean?"