Soot from drain hole in exhaust question

[Graydog]

When my bike is warming up in the driveway I always find a black (soot) spot on the gravel under the drain hole (pin hole) on the exhaust. No smoke from exhaust under load or just idling. I am also getting poor gas mileage (about 55mpg). Plug is not brown as should be...it is slightly black but not built up black and not white at all. I recently plugged the eight holes the previous owner drilled in the exhaust. I dropped from the 58-62 mpg I was getting to the 55 mpg I am getting now. I have run several tanks to make sure of mileage. Bike runs much better with the holes plugged. I have read here about re-jetting the carb after plugging the holes but talking to two Suzuki mechanics at dealerships they both say the same thing....no. Both looked at the carb and agree it has not been "broken down" and is still original condition. (one did the make ready when the bike was sold to the first owner, knows the first owner, and assures me the carb has never been tampered with. He also did the break in procedure after required mileage on this bike for the first owner and the make ready for me when I bought it.) I have not questioned either of them about the black spark plug (I looked at it after they had looked at the carb and suggested I take it out and inspect it). both agree sometimes valves need adjusting after break in but that is very rare.

Bike has 1500 miles on it and is an 07. Before I call one of them Tuesday and tell him the plug is "sooty" but not crusty black I wonder what your opinion is on the poor gas mileage? Normal speed for me is 45-55 on country roads. Bike runs great.

Thanks,