Good luck getting any contact from Chipwizards, I've sent countless emails to them and never once got a reply. I believe they are aircooled experts but never heard any watercooled feedback.
As for price, £3-400 is wishfull thinking, REVO and GIAC start at around £700, DMS is ALOT more and all only quote +25bhp results when included with an improved exhaust package. I'd be very surprised if you could get +30bhp for only £400, infact I'd be shocked. Sorry to sound so cynical but you just don't get that kind of increase for nothing... Also some re-mapping can be detected by your OPC and if found will invalidate parts of your warranty. Look into this before commiting to buy. The only power upgrade that OPC will 100% honour claims on is the X51 pack (381bhp on the 7S), and you're looking in the high 4 figures...
This is all just my opinion (together with alot of online research) I'd be very glad to be shown otherwise though as I'm looking to do this early in 2009...
Check DMS automotive, Porscheshop, Parr, Design911, Regal-auto, Oakley design, 9m, and Fearnsport amongst others
Good luck :thumb: