RB4 like a WRC car would be like an overkill...
FXR is ok for me, as a WRC car...
what I highly recommend: Let the user add own samples for the other cars as well (via "if FileExist("XRR_bla.wav") enable(XRRsounds)")
All in all, I love the soundmod, yama, and keep working on it... 24/7, you don't need any sleep or food or real-life(tm)
edit: oh and btw: indicator doesn't seems to work for me