First make sure to remove the mebrane from the inside of the ribs. You can't do it with frozen ribs so thaw them in the fridge for a couple days if they are frozen.
Make a dry rub with a generous portion of chili powders (I use ancho, chipotle, and sweet paprika, whatever I have around) brown sugar, garlic and onion powders, salt and pepper, and maybe some cumin, cocoa powder, cinnamon, nutmeg, whatever you feel like. I hate to be so vague about this but I usually eyeball - maybe 6 or 8 tbsp of combined chili powder, about the same brown sugar, 1-2 tbsp of onion and garlic powders, 1 tsp of salt/pepper and less of the other flavorings, for 4 racks of ribs. Make plenty of rub and really coat 'em good.
Before you seal the vacuum bags put half a teaspoon or so of liquid smoke in with each rack of ribs
Sous vide for 36 hours at 145 degrees F, turning the bags every 6-12 hours to evenly distribute the juices.
Open the bags (you can save the juice to make a spicy bbq gravy or spread on toast if you want, but there will be a LOT of it) - I usually cut the ribs in half either at the beginning or now, because otherwise they will fall apart. They are very tender at this point.
Grill them at a relatively low temperature while carefully flipping and coating both sides a few times with barbecue sauce, allowing the sauce to carmelize.
Slice into individual ribs, serve with lots of napkins.
This is a great guide to consult on sous vide ribs of various temps/textures: http://www.seriouseats.com/2015/09/the-food-lab-complete-gui...
I don't use sugar as I try not to eat it, so I substitute stevia. Sugar would change it quite a bit (possibly for the better). This is the only major change.