Thes chips are popular with EURO boys, the general consensus seems to be 'buyer beware'.
If engine conversions do not wet your pants, and you already have CAI and extractors / exhuast - then a either a chip or cams are your last options for a tad more oompff.
There are some people who get stooged and think the chips are wank factor - but if the people selling them cant convince you, no one will...
**Important**
Guard your own back (read: wallet) by making the 'authorised installer' quiet clear if it doesnt live up to your hopes, you will be getting your moeny back.
If it really works they wont need to worry... will they?