I just found this thread this morning and see you found the issue. I knew something wasnt right with that particular bow because the new bengals are very quiet. my friend just set one up 3 or 4 weeks ago and doesnt have any limbsaver or string silencer and is quieter than average bows with add ons. It is a very nice bow for the price and he is shooting leaps and bounds better than with his older PSE.
Im glad you found the issue and are happy with the Martin bow. I will tell my friend about the sts helping even more.