The fuel mat was decent when it worked, allowing me to run down to about a quarter tank. After a while (installation error on my end) the hose came out of the oem basket though and the car was operating as if I didn't have it at all. So it's more prone to bad install.
I definitely wish I went CJM or Radium from the beginning though, since when it stopped working, the mental burden of having to worry about fuel consumption and the hassle or bringing several gas cans to the track all the time was a drain on each track day.
As far the the car feeling soft, my opinion is that soft suspension helps build good habits. Tires may be worth replacing with RS4's or SUR4G's when the ECS's wear through, just because 300tw tires often get too far above their operating temps at the track and you may end up getting less time per dollar on them than jumping to higher temp range track oriented tires. Anything to make the hobby cheaper and let you get more track time
