I replaced my glowplugs in the 603 the other day and noticed when I took the manifold off, my valves and ports were all covered in a thick brownie batter like soot, I had to go into deep meditation to keep from cleaning them but i did resist and just put the intake back on. I was not sure of the side effects if I were to just soak it all with brake cleaner and let it set overnight. 2 ports were real bad the other 4 were just real sooty. Does all that soot affect the performance that much? Shes got about 320k and runs strong and smooth, but does have some sluggish days for some odd reason. Any suggestions on how to clean this mess or should I just live with it.