This annoys me, but in a different way than most people I think.
First off, most of the people who modify their exhaust are doing so on 4-cylinder engines. The idea is to make it sound like they have a powerful engine I guess.
Right there we know they have massively failed. Any properly tuned 8-cylinder (or more) engine in good running condition will put the lie to this. There is a throbbing, vibrating, low frequency sound to these sorts of engines that no 4-cylinder with a modified exhaust could ever replicate.
So the fact that they are trying to do this and that there is no way they ever could confuses me. Why would you try to emulate something that is simply not possible with the type of engine you have? Are you trying to compensate for something?
THEN, the noise that these overworked hamster engines generate is also loud and annoying. So now I'm annoyed, not only because of the sound but because these people are trying to make me believe that they have some sort of 'powerful' car.
They aren't fooling anyone.
If they went to a real car show with true muscle cars they'd know that.