Buick rendevous big noise

Today, a mechanic replaced a bracket holding the muffler pipe so that it wouldn’t rattle against the drive train. That eliminated the rattle, but now the car sounds like a teenage muscle car. Mechanic put it back on the lift but found no muffler leaks or errors in torqueing bracket. Why do you think the sound of the car changed so dramatically? Generally, loud at low rpms and when I accelerate. thanks for any advice!

Did the mechanic use a bracket that included a rubber isolator?

That I don’t know, but will check when I take it back on Monday. How much of a difference does it make?

I would suggest that when your mechanic was working on the exhaust system he caused it to shift sideways. This could have easily caused one of the gaskets to shift or tear causing your exhaust leak.