Soak the wood chips in water for one hour. Drain the chips and place in your smoker box, or fold and seal inside an 18" x 12" piece of tinfoil. If using foil, poke the packet with a fork to allow smoke to escape. Heat your barbeque to medium-high. Combine the chili powder, cumin, paprika, salt and pepper in a small bowl. Stuff the cavity of the chicken with the onion and garlic. Rub the chicken with the spice mixture. Set the wood chips directly on the coals on one side of the barbecue. Set the chicken, breast side up, on the grill on the other side of the barbecue. Close the lid and turn the heat off underneath the chicken; leave the other side of the barbecue set to medium-high. Barbecue the chicken for 50 minutes, or until the temperature in the deepest part of the thigh registers 170 degrees F on an instant read meat thermometer. Brush the chicken with the barbecue sauce and let it heat through a few minutes. Transfer the chicken to a plate, rest 10 minutes, and then carve.