I had a terrible experience this past festive season. I took a 650 km drive to the coast, which was great. But, while at the coast, the exhaust on my M3 suddenly sounded extremely loud.
This started on Christmas eve, so I was stuck without a car on Christmas eve, Christmas day and the following day which is a public holiday in South Africa. During these three days all car dealers were closed, so I had no idea what was wrong with the car. It drove me crazy! I thought I blew a gasket or cracked the manifold on the car.
Bright and early on 27 Dec, I was at a BMW dealer. They put the car on a ramp and immediately told me that the exhaust was leaking due a campaign that was done on the exhaust in 2009.
The dealer explained that the pipes were originally connected with a piece of metal, but that caused a rattle and did not allow the pipes to expand, so BMW decided to do a campaign on all cars and remove the metal piece. Part of the cut metal is evident from the image below.
As you will see, the other metal piece broke off, resulting in a long slit which caused the loud exhaust. BMW did replace the exhaust under warranty, but it was very irritating that this happened while I was on holiday!
Here is a photo: