so it sounds like theres a hole in your muffler? did you check your exhaust piping? just make sure its not that...

 

There is no hole. Mechanic's said it will come back to normal in a few days, but it hasn't, it seems to be lees noisy when warmed up. Is that a normal occurence after a timining and balancer belt changes, thevolume of the engine noise changes, increases? Why would that happen?

 

Hmm i just had my belt, water pump, spark plugs, gasket, and the other belts done and my car sounds the same. I got mine done at the honda dealer.