I might be inclined to believe foxhound if he didn't weigh less than 40 lbs. That And neither a lab or a foxhound have a tail that goes straight up and curls over the back.
Whippet is a possibility, but again that doesn't explain the tail curling over the back. Granted his tail is longer and not as bushy as a pure Basenj, but then he isn't pure Basenji.
Pugs have a wrinkled forehead and a curled tail, but he has the longer neck and a gait more like a sight hound, and his coat is shorter but not the double coat of a lab, so I am kind of ruling out pug.
He may be a big pile of mixes from parents who were mixed. I don't really care what breed he is, he is a great dog. I think I am right on basenji, but if not, it's no big deal. And no he hasn't chewed my underwear. He did chew on the couch cushion where I usually sit.