My exhaust revs up fine with the clutch in, as well as if its in neutral. But whenever I am driving in 1st gear and accelerate fast my exhaust seems to kind of bark rapidly. I think it started doing that after I was driving on a rough gravel road and it scraped under my car. I went underneath and tightened my mid-pipe flanges as best I could but it didn't seem to help. It seems as though it only does this in 1st gear from the torque. Anyone have an idea on what it could be?