engine or exhaust..roaring noise

a few months ago I noticed a "roaring" noise when I would drive in rain.
came from front right side of car('92 240 sedan). I have new Michelin tires
and that's not the source. Just had my wheel bearing checked and he said it
was "tight."
Friday I started having a more intense noise. I had my exhaust checked and
found two holes in muffler..replaced.
Now after the car drives for about a mile I am getting a "roaring" noise
that seems to be coming from right front of car. Also, when I rev the motor
sometimes it backfires and there is a knocking that seems to be hitting
under the driver's side that I can feel. Very strange.It does not occur when
I first crank the car but becomes worse after a mile or so. Sounds like a
hole in muffler but I know it can be.
I've looked under hood and car but can't find anything out of the ordinary.
Sorry for the long post.
Any suggestions?
thanks.
JB

 

Feel around the exhaust manifold when you first start the car, do it when
it's cold and be careful as it gets hot surprisingly quickly. The idea is to
feel for exhaust leaking around the gaskets or through a crack in the
manifold.

 

A method I have used is to connect a shop vacuum backward (so it blows air
at low pressure) to the tailpipe and feel for the air coming out. Mike F
pointed out there is a potential for getting dirt in the exhaust - could be
bad for catalysts and other sensitive stuff - so be sure the vac is empty
and let it exhaust the residual dust into the air for a minute before
connecting it.

Mike

 

thanks for the information!
JB