Absolutely great. If I were to make one minor suggestion: when sitting idle in neutral (like in the pits when playing with car setups) the sound becomes very repetitive and almost like a little song (d-duh-d-duh-d-duh-uh-uh repeat). If there is any way to make it a little more random, or make that idle sound a lot longer and varied before it repeats then I think it'd be even more awesome.
If not obvious I have no idea what I'm talking about or how to do any of the above... but I hope you can! Nice one :-).