I know. The F1, Murcielago, LFA, Zonda R, and Enzo all sound the same with the racing exhaust. But I rather have that same repetitive sound in the Aventador since it's a V12 sound, than have an Aventador sounding like it has a V10. I don't know how others can play like that, for me it just ruins the realism. If I see a car that doesn't sound like it's supose to, or can't be fixed, I simply don't play with it.
I usually choose the exhaust that best replicates at least the type of engine that the car has. Most likely it will be the stock exhaust. I've heard a lot of LFA's online sounding like V12's, Toyota 86's sounding like they have a six cylinder engine, Vipers with a strange and undefined sound, M5's sounding like V8's, and the list is endless... That really enrages me, but I understand that everyone is free to do whatever they want in the game.