I think you may want to do more homework before you have a chip fitted. You'll also want to check out Dinan chips. Search posts (across all forums) as there's plenty of discussion...including bringing into question the true hp increase these chips provide, the impacts on the engine longevity, gas mileage, and certainly the need to run a high octane gas (depending on your model, you may not need to run high octane now).
<span style='color:green'>1994 325i </span>- - - 75,000 mi.
No mods - - - very happy as is!
<span style='color:green'>1995 525i </span>- - - 154,000 mi.
No squeaks or rattles... unreal!