Originally Posted by RPM WS6

The only problem is that these cars didn't have this condition when they were new and stock off the assembly line, so something has changed (internal wear, or something such as this) over the years to cause the issue (unless there is some modification that's been done which led to this side-effect). Hopefully your tuning changes continue to compensate for whatever the problem is, but there had to be something worn/out-of-spec which caused this in the first place.