Not sure if I'm the only one having this problem, but thought I'd post what I did to resolve it just in case another person has the same issue. Maxxforce 10 motor.
The sheet metal guard surrounding the muffler was rubbing against the the piping from the turbo coming down to the turbo cooler.
When I took the MH to the International repair shop a few months ago to get the antifreeze changed out, I had them loosen and readjust the turbo pipe so that it was not contacting the muffler guard. On a recent trip, I noticed that it was rubbing again. While performing some other maintenance, I replaced the rubber boot on the turbo piping and used the old one as a spacer/pad to prevent damage to the piping from rubbing the guard. I split it and wrapped it around the pipe securing it with the old clamps. Hopefully this resolved the issue.