First Running Issue in 24K miles Options

[Bulldog9]

Took the day for a drive yesterday, about 8 hours and 250 miles. First half was mostly twisty roads in the Northern Blue Ridge, and wanted to get home as the sun was setting and temps dropping (34degrees), and I still havent done the heater blower.

I took the super slab and was cruising along at 75-80 mph for about 45 minutes, and had a sudden stumble, intake pop and black smoke out the rear. The car continued to run and I made it the last 70 miles home with a sluggish motor, and occasional intake pop. Haven't checked anything yet, but I am thinking coil or ignition. Didn't seem to be any specific cyl, and the intake pop was moving around. Also the idle is a little stumbly but stable. I don't think it is carb related as the change was sudden, and no settings were changed, and I have about 500 miles on the car post recent Tangerine cooling fan install.

I'm running the Pertronix Billet Distributor, with Flamethrower II and matched coil. One thing I did notice was that the coil lead was loose when I disassembled and reinstalled. I cleaned up the connector and spread out the connector, but when I reconnected it didn't have that satisfying click. I was thinking it may be the coil itself too, or even the power to the coil, but not ruling out a gas related issue. I was about 50 miles into a fill up. Once temps are up I will start working through it.

Appreciate any thoughts.