Sorry for my bad english.
I´ve made a sound file and hope that you can hear the problem. In the sound file you can hear the XRG, but i have this problem with a lot of cars but not all cars. ??? It´s only if the engine in CSR is ON.
In that case I don't know, sorry.
Anyway here is a preview for my new FZ5. Samples taken from onboard Porsche footage. I know you may find it a bit too subtle, but don't forget that its a road car. Also the crackling and bad quality is due to my laptop's crappy soundcard, my desktop PC is not with me.