Finally!
Done this as an attempt to highlight the left channel from the right one out of a RR3 clip (we were discussing this (sort of) in the stereo topic: http://myrealracing.club/thread/2416/stereo-car-sounds).
However, the result also happened to be actually a cleaner, enhanced sound. I'd love some feedback on this - hopefully, you'll notice the differences!  Grab a pair of headphones ;-)

How to: if you want.... (Edit: if both videos play at the same time in this window, just start both and jump to step 2. Otherwise...) 
1) open each video in a separate tab (or this post duplicated in two tabs), push play on both at the same time, and
2) keep muting/unmuting the first one, which has all "noises" of the original track.
This way, you'll notice how much garbage is polluting the soundtrack and, once you mute the original, will identify the details of each channel.
Alternatively, grab the two attached mp3 files and open one in each music player instance.

Check out this pair of preliminary videos (I'm new to Reflector software :-/) The first one carries the original track. There's is too much going on and the sound is not good in inexpensive headphones, much less in small speakers. The second audio isolates better the cars passing by, and even the revving of the car I hit in the beggining is clearer.

Needless to say, most of the sound goes to one side when you turn around slowly (starting at 00:15), and this was the clue that some essencial stereo separation was going on. Take a look at the plot for the original left and right channels for that section of the video.

My "enhanced" track is an attempt to enable only the extremities of the stereo track, i.e. play only what happens in either left OR right channel at every instant, filtering off what would play in the center. ...and turns out that fraction in the middle is quite a noise!
I just used a little free program (Audacity) to separate the channels, invert one, and glue them back together so what plays in both channels at the same time is cancelled.

Most of the original effects are actually quite hard to notice if you don't pay a lot of attention, since those Monkeys piled up so much noise, so I believe my enhcd track sounds better.... except for a few details. Sometimes...
- my own engine sounds too low;
- the noise of loose broken parts have a short delay between the left/right channels, so it get distorted in this method;
- by highlighting the extreme left or right, the sound comes out a bit "fantastic", although that was my first goal in this project.