Black sooty condensation from exhaust when starting

I've got the car all tuned, new carb which has been adjusted professionally, and starts, idles and runs out fine, but after sitting for a few days, when I first start it, small amounts of black sooty water shoot out of the tailpipes. After driving and warming up, it doesn't continue when starting again. My oil level stays full, as does the radiator, and the oil is clean with no sign of water.
It is the original '67 318, with 43K original miles and never rebuilt. Engine sounds fine as well.

Does anyone have any idea what may be going on with it?

Thanks!