Hi I have had my 535d remapped and would highly recommend it. It makes an already impressive car brilliant. Fuel economy improved by about 2-3 mpg, if I don't use the extra power. No issues with reliabilty. I used JamSport in Northampton who have a nationwide clientele, they also dyno'd the car for me too. They have tuned two of my cars to date and are about to do a third...and I'm very fussy! I declared it to my insurance and my premium increased by £25 per year, with which I was pleasantly surprised. MOT is fine and two years ago it cost me around £600 which included a hand held box, that I can use to put the car back to stock (and back) if I wish and before and after rolling road. Is it worth the money...OH YES!