The Simota I fitted made a very noticeable difference to mine, the car feels smoother to drive and pulls a lot stronger. The big difference is 3rd and 4th gear.
Before fitting, 3rd gear would lurch going into a corner, like the car was being starved of air and seemed to de-celerate in a very jerky way. This has now disappeared and keeping in 3rd is very smooth, it is loads more fun to drive.