First, the sauce: Mix together the cola, the ketchup, the coffee, the molasses, the vinegar, the Worcestershire, the chili powder, the salt, the garlic powder, and the onion powder in a medium saucepan over medium-low. Cook while occasionally stirring until the sauce is heated through and flavors meld. It should take about 30 minutes total. Remove the sauce from the heat, and let it cool completely.

Pat both sides of the rib slabs dry with paper towels. Using a sharp knife, remove the thin membrane from back of each slab by slicing into it and pulling it off with a paper towel. Don't be afraid to ask a butcher to do this part for you.

Combine salt, coffee, pepper, paprika, and chili powder in a bowl; rub both sides of each rack evenly and let stand at room temperature for 30 minutes.

Prepare a charcoal fire in your smoker according to manufacturer's instructions, bringing the internal temperature to 250°F to 275°F. Maintain temperature for 15 to 20 minutes, then place the wood chunks on the coals.

Place your rubbed ribs, meaty side up, on the smoker and cover with the lid. Smoke the ribs, maintaining an inside temperature between 250°F and 275°F until the meat begins to pull away from bones but is not yet tender, around 3 hours. Brush about 1/2 cup of your sauce over both sides of the ribs. 

Cover and smoke until a meat thermometer inserted in between the rib bones registers 205°F and the rib meat is very tender, about 1 hour and 30 minutes, brushing with about 1/4 cup barbecue sauce every 30 minutes. Remove ribs from the smoker; brush with 1/4 cup barbecue sauce. Serve with remaining barbecue sauce.