I remember after I first played San An I loved the driving physics so much in comparison to GTA 3 and Vice city, where the cars are instantly at top speed and turn straight away. But a large open map with LFS physics would make a perfect game.
Not necersarily on downshift, but when the revs of engine go from high to low generally on higher powered cars.
In this video you can hear it, but can't see it: http://www.youtube.com/watch?v=tFrvMfjgxU4
In fact I can hear it on my lawn mower, but it can't be seen.