I had my bora TDI done by Chippeduk, they are based in bromsgrove, have a very good reputation with the BMW/supercar crowd, he has even chipped ferraris etc, my car went from 130 to nearly 180bhp, cost me £250. On uk-mkivs.net forum I know hundreds of people with remapped cars and they all love it, there is no detrimental effect to your engine, if you abuse it it will last less whether it is tuned or not just remember to let the engine warm up before giving it any beans and service it regular. What engine is in your car? if its the AGU your looking at 190-200 bhp, if its an AUM then your looking at 212-220.