I would like to see better tyre smoke that hangs in the air for longer and is much thicker.

search for smokemod

a fairly simple change to the particle acceleration (giving it 0 velocity instead of it being shot out by the tyres) would be a nice start. Smokemod didn't really improve anything to my eyes.

I agree, the smoke generation doesn't seem right, but I think is one of those eyecandy things that will be improved after S2 (I hope )