[thstone]

First, crap welding and fiberglass being blown all over the back of the car is normal with these inexpensive cat back mufflers. Luckily, the fiberglass phase doesn't last long.

In regards to the sound, I am hard pressed to think of something you may have done during the repair of the flex section that would result in a restriction so severe that the sound would be severely muffled. I mean, its just pipe connected to pipe, so it should be fairly obvious if you did something wrong. Again, I am assuming that you either repaired or replaced the damaged flex pipe. Nothing else changed, right?

If so, then my first thought is that you got used to the unmuffled sound (which is L-O-U-D). Now that its muffled again, it may sound that much quieter because you're comparing it to what was basically an open exhaust.

Another explanation is that previously you had an exhaust leak where the flex section mates to the rigid components and that leak was causing additional sound but was (inadvertently) fixed when you replaced/repaired the damaged flex section; so now it sounds quieter because it is quieter. I had this exact situation when I didn't get one of the connections between the test pipe and the u-pipe to seal properly.