So, I think Live for Speed's sound engine is very great, but there are somethings missing. Like exhaust crackling and pops.

I think the effects of exhaust crackling can already be achieved currently. You just need to have a damaged engine. With that, the engine will give off a very very subtle crackling noise (even when on throttle)

I wish to hear this detail on LFS, being off throttle always sounded way too clean