Go to your lfs\data\audio directory and move message.raw and sys_message.raw to somewhere else
I really see no need for karts, IMO there's a huge gap in the sim-racing market for historic racing, seeing as there's plenty of competition (GTR, rFactor, Fir$t) with GT type cars, with maybe a smallish mid-engined V8 (Ferrari 360 style) and a slightly bigger single seater (F3) then most of the current simulation market is done (assuming Nascar and GTP aren't going to be beaten by LFS anytime soon).