Zipperfoot,
In response to your question about always seeking car improvement.
Here is my 2 Cents.
Many people find it hard to believe that their car through some modifications can't really be improved any more. Its human nature to want to think you have the ability to always improve a device (car in this case).
Part manufacturers will always try to make improved parts (so they say) even though by just driving a bit more carefully or skillfully will result in fast laps.
As much as anyone wants to think, these cars do have some wiggle in suspension parts, wheels, etc. Does anyone think that a very minor part such as a thin washer in a suspension piece will make that much difference when many suspension parts have some minor play.
We all want that slight advantage over the competition, I find the hobby to be enjoyable when I relax, enjoy my race friends and realize this is whats important, not a 1mm play or adjustment on a small part.
Track conditions, tires and tire wear, and driving skill make more difference IMO.

Rick