I have a 1995 Accord LX - 4cyl, 4dr 5 spd manual - At 110k the exhaust got real loud very suddenly. When I took it in to a nationally known muffler shop they told me the center pipe was shot. Got that replaced but when I drove to work I noticed that every time I downshifted or backed off the gas it was quite loud and sort of bassy...as in when coasting down a hill or slowing to a stop light it goes HMMHMMHHMMMM ...(probably more noticeable inside the car than outside).

Took it back and they tightened some gaskets - no better. Took it back again and let them replace the muffler. ka-ching! Still no better. The car definitely sounds worse than it did right before the center pipe broke.

What could cause this? Could it be due to an incomplete or inferior replacement? (The shop, of course, insists that they have done everything they could.)

Help - I don't want this car to sound like a hot rod! Looking for any ideas on what to try next?