the aeroplane leaves long trails of black smoke everywhere it goes.
I've had that too. Received calls from the tower. Ours has been adjusted since then, but I still believe its richer at full power than the Continental "max allowable rich" graph. Thus I want to intervene manually to get a better condition.
If you have ever read the fuel flow adjustment procedure for a turbocharged engine it is quite complex, time consuming and requires calibrated gauges. I believe that hardly any LAME's do this and I suspect that few actually have the proper calibrated gauge set up. They just tweak it from the last position and ask the owner to report back. Proper adjustment requires full power climbs to the critical altitude - when is the last time that was done as part of a 100 hourly??.
But, I also think I'm discovering that the Continental fuel flow curves don't match (ie conflict with) some of their other specified operating limitations. This is the sort of thing that might happen if some data (ie the fuel flow curves) came from dynamo-meter run with perfect cooling and some restrictions came from real world testing and some came from good old fashioned boiler plating by guys sitting behind desks wanting to be conservative and add safety factors. - Which is the point John Deakins has been making for years!