Can neither be a good answer.
Polk Performance is a good dyno shop. I dont know if I would let them tune my truck since they are import guys, but David Polk is a great guy.
Mann Performance is a good machine shop.
Welcome to Arkansas. Thats how it is around here. If you want we can meet up one day, friday night we should be out roaming around, if you want to meet then I think there is a guy that may have an idea what it could be. It may just be the exhaust, i have a small pinhole leak that I hear when I start it up.