Noisy exhaust - Alfafan {P}
My son recently bought a 306XSi which is in excellent nick. The only problem is that a previous owner fitted a "boy racer" stainless steel exhaust with a large diameter tailpipe. The thing is that it produces an annoying drone at normal cruising speeds. I'm sure that if he went on a trackday, the car wouldn't pass the noise tests.The exhaust is in good condition so he doesn't want to spend money to replace it.

Has anybody got any ideas how the noise can be reduced?
Noisy exhaust - Dizzy {P}

As you probably know, exhaust systems are 'tuned' by the car designers for the best power/noise compromise. In my opinion, the previous owner's fitting of a big-bore has possibly REDUCED the power output by upsetting the designed back-pressure, unless the original tailpipe was grossly undersized.

I can't think of any (sensible) alternative to simply cutting off the existing tailpipe and having it replaced with one of the correct size (perhaps a length of stainless tube). This should reduce the drone whilst still looking good and would save the cost of a complete new system. Might still be a bit noisier than standard if the silencer isn't fully baffled (i.e. if it's what we used to call a 'straight-through').
Noisy exhaust - simmo
Not ideal, but cheap. We used to remove the fibreglass wadding from our 2 stroke bikes years ago, to make them straight through. What about the reverse. this would certainly alter the mix though, as exhaust technology makes use of a pressure pulse to assist in fuel efficiency.
Noisy exhaust - Another John H
If the add-on is in good (shiny) condition it probably has a secondhand value, which might help balance the equation a bit...

Value my car