[byootox]

Well the engine needs to be in a good state of tune beforehand.
E.g. fully serviced and making sure it drives well already with no fault codes or other problems first.
Other things like a clear breather system, timing belt and boost hoses and clips in good condition etc.
I'm not sure exactly what the bsr stage 1 includes but 299bhp sounds a bit optimistic for a stage 1 tune on one of these.
Best bang for your buck is a remap with decent downpipe, that should free up an easy 40bhp over standard.
Don't get too hung up on exact bhp figures etc, real life driveability is far more important.
I got mine done about a year and a half ago and the only things I've had is rotten hoseclips burst with the extra pressure, but pennies to fix and easy.
The other thing to remember when you take it is fill the tank with super as that will help set a map better without pinking etc.
Not essential but best if the place thats doing it for you has a rolling road so you know what power your starting from.
Most people don't realise that there car will have lost some power since it came out the wrapper so to speak thus my comment about not worrying too much about power figures unless there is a drastic problem to start with.