Twelve - or better yet, 24 - hours in advance of grilling, cover the pork with a fifty-fifty mix of sugar and salt, wrap it in plastic, and refrigerate it.
One hour before grilling, remove the pork from the fridge to allow it to reach room temperature. At the same time, soak the woodchips in cold water, drain them and wrap them in foil, poking a few holes to release the smoke.
Start the grill and set the burners on low (you want to maintain a temperature of 250 degrees, no higher) and place the packet of chips under one of the grates.
Turn the center burner (or burners) off, place the pork fat side up on top of the center grate, set the drip pan underneath, and close the cover.
After five hours, begin checking the internal temperature of the pork. When it reaches 185-190 degrees and the meat is fork tender, transfer it to a cutting board, tent it with foil and allow it to rest for about 15 minutes.