240Z WILL NOT run right

Things are looking up.  Here's a driving clip from earlier:

Work done:

• TIming to 5° BTDC @ 750 rpm.
• Rechecked cam sprocket mark (this is at TDC):

• Cleaned spark plugs.  Here's before:

Mixture nuts still set ~5 turns down.

Still running off the auxiliary tank.  I hooked up the main tank just to see if there was a difference, and sure enough, fuel pressure dropped and the float bowl on the rear carb ran dry.  Definitely think there's an obstruction in the lines or the tank.  Going to drop it and have it re-cleaned.

I drove it to the gas station (3 miles one way) and back and it only backfired once under heavy load.  It felt REALLY good to have been able to get it out of the neighborhood.

So yes, the exhaust is pretty sooty.  Is this typical?