Owned a FiST for 2 years before trading it in for a Clio200EDC last year. Same reason as you
Through the corners, they are both very good. I got both cars tuned to stage 1, the Clio made more power and the FiST made more torque. Clio after the tune is definitely faster in a straight line than the FiST but by the time you get the sensation of speed and look at the speedo you will be way over the speed limit. The FiST on the other hand will feel faster than it really is (bit like the older Clio's).Tuning the Clio probably will cost a bit more than the plug and play Bluefin. There are plug and plays available but I will recommend you get it tuned by Racespec(Ace) and preferably on a dyno.
I only had the FiST until 30k km and the Clio is currently at 20k km so cannot comment on the possible high mileage issues.
PS- I miss my FiST a lot - Will definitely buy again!