Good point; I've never used the Berryman's in the crankcase of my Contour. I've only used it in the crankcase of my '86 Cavalier, which already has a bad engine that I wouldn't have minded screwing up. While it didn't screw up that engine, I'm not sure I'd use it in the Contour. I just use synthetic oil to keep my engine from sludging up.
As far as the "combustion cleaning system" from Berryman... I've used that in the Contour, and it's really the same thing as the "easy" intake manifold cleaning. It just makes the process easier because it includes the plastic tubing to make all the connections; you don't have to use pliers to control the solvent flow. That's the one that reduced the noise for me.
