Well I have to say that having recently paid £90 to have my X-Type 2.0d Terraclean-ed (if that's a word) I am very happy with the results. My reason for having this done were twofold; 1. black smoke on acceleration - all but gone, still al slight amount but nothing like it was 2. Slight hesitation whilst cruising, ranging from almost unnoticeable to quite violent, no loss of power though - this has gone completely. This alone was worth the £90. Terraclean claims; improved mpg and pickup on acceleration. 1. improved mpg - jury still out but it appears to have improved a little. Only done about 150 miles, need at least a months driving to be sure. 2. Improved pickup - again jury still out, I "think" I feel a smoother acceleration but this could be psychosomatic. Not sure if I will ever know as I had no data on acceleration just prior to the cleaning process. That's all Folks