Noticable difference in performance, turbo spools up at around 1600 rpm now, and you can really hear it whistle. When I put my foot down, I get a good kick and she pulls like a train. Obviously, your not going to achieve the sort of performance you'd get from remapping a TD5, but it's still pretty good.
As for economy, its given me around 2-3 mpg. May not seem like much, but over 10000 miles that makes one hell of a difference! For £20 (inc delivery) you can't go wrong really. I'd recommend you grab some plus gas off ebay aswell, works wonders on the bolts!
HTH,
Lew