drtchock

and would i have to tell my insurance company?

also what results could i expect performance wise?

SineSTI

Just remap? Or some other modification? With new exhaust (downpipe, central section and backbox) something about 330/340 ponies. Just remap, maybe 300.

Beastie

iTrader: (2)

Remap will normally be about £600 but if a group buy exists you may get for £400. You should be able to remap to 340bhp but will need an upgraded fuel pump and more free flowing exhaust.
The Prodrive performance pack can take you to 316Bhp for about £1800 and you will retain your warranty.

You should tell your insurance company.