Do you know what boost it is running? Does the boost gauge (centre console) go off the scale?
To get to 292bhp (if that's what this means!) you would need to be somewhere up around 1 - 1.1 bar.
May well be the ecu has been chipped to up the boost and alter the fuelling. If it has, that chip will not be mappable (by yourself at least). Removing the chip should return the car to stock..... as long as you don't bugger something up removing it
Hard to know - have a look at the ECU and see what stickers are on it.... usually a chipped ECU will have an additional sticker on it. ECU is under the centre of the dash... i.e. stick your head in the footwell and look to the middle of the car! Not the easiest thing to get too.
Could also be worth looking under the bonnet for any changes made to the vac / boost pipes to the turbo.
Cheers
Graham 8)