you need to buy what they call a tuner muffler. They run from $129.99 and up.
It depends on the smell. Generally, the exhaust has no real odor to it if everything is working right. A "rotten egg" smell is a sign of too much fuel entering the catalytic converter (which will...
there is always exhaust (expect when the engine's off or hybird)unless you are too close to the car in front of you.
usually a loose bolt
make sure your car isn't to low because the exaust might scratch the ground and brake
Maybe slightly do to echo, but mostly just changes the tone. to increase decibel, would have to change muffler.