Hello, I have a 2006 Mini Cooper S, Automatic, Super Charged (not turbo), 91,000 miles (20,000 of those are mine). I believe I am about to deal with a carbon build-up problem and from my online research I am finding this is seems to be a common and not cheap to fix problem. Wondering how others have dealt with this and what advice one might have. I am in the process of setting up a compression test, so i do not have that piece of evidence. Basically the check engine light keeps coming on. Code indicates a misfire. It can be reset and will come back on after a couple of weeks. I have been told that someone else with this same issue was quoted $3500 - $4000 by the local dealer to fix (no way). I do not know if there may have been other issues at play in this person's situation. Another local mechanic has quoted me $1200 to fix (big ouch). I keep reading on line about the cleaning with walnut shells which should run about $600 to $800 (still hurts but better). Is there any place within a reasonable distance (Atlanta - Charlotte) that offers this? Is it worth it? Car drives fine. I can tell nothing is wrong. Previously I have tried some Techtron additive and was told to drive it hard. I imagine people on around me think me to be the obnoxious driver, but I am driving it hard. I always use Premium gas. I have read threads on other sites which indicate this can be an every 20,000 mile issue. Is that true? Wish I had seen that in my pre-purchase research. As always, any advice, help is welcome! Thanks a bunch!