There are many tuners, Revo, Custom-Code, Superchips, GIAC etc. They are all very good, I have only heard good things about them. Just make sure that if you do have a remap you get before and after rolling road runs so you can see the results
I don't know where you are based but Awesome GTI in Manchester are doing custom diesel maps at the moment, the map is tailored to your individual needs and you get before and after rolling road runs included in the price. I have spoke to a couple of people who have had this map done and they speak very highly of it. It costs £375+ VAT
