my friend has a 1991 ACcord and all of the sudden the exhaust got quieter...
why?

btw: If a cars Stock Headers are cracked, will the car respond slower?

 

Collapse of part of the catalytic converter block might cause a reduction in noise level. Shake it to see if it rattles. If yes, that may be the problem.

good luck

 

If the exhaust manifold is cracked then it will be louder, by the way if you are refering to the 91 accord it would only have one exhaust manifold/header, an inline motor usually does not have two, usually only a V type motor will.