Yeah I agree the plug looks kinda dark which I suppose should really be kind of a light tan color but then all the plugs were like that in Dec. If its rich, maybe its not due to excess fuel but instead limited air? The FI company first inclination was the valves in the throttle body could be the culprit. It appears easy enough to take a stack off and see if anything looks odd especially for that one cylinder, although I suppose that could be a longshot. I suppose I could also put my hand on top of each individual stack and see if there is any change in engine sound (spitballin here). As you say the stethoscope didn't prove anything either but at least nothing sounded different from engine side to side on the fuel injector, head or valve cover so at least the fuel injector is clicking. In looking at how to do the compression test on that one cylinder I don't really feel like taking all the plugs out again, finding the fuel fuse, disconnecting the coil. I thought I could just hook up the gauge to that one cylinder and turn it over 3 cranks prior to start and read the gauge.