"breaks down" into a horrible single pitch noise at about 5000RPM. At
6000RPM, the sound is a single horrible noise, and stays that way all way up
the tacho.
The interesting bit is that this only occurs about 40% of the time. I can
often fix the problem by quitting the current session then going back into
it. The problem will either be there all the time during a session, or
never.
I am using one of the popular sound upgrades that provides different sounds
for each car. Unfortunately, I can't remember what I'm using or how to
restore the original sounds.