coletrickle

First of all hello to everyone on the forum, this is my first post and I'm sorry its a question!

I have just bought a 52 plate UK bugeye Impreza WRX wagon today and already I have a problem!! I test drove the car first and it seemed to drive fine, not as fast as I had expected but this being my first Impreza I thought it was OK. I drove it the 60miles home on the motorway with no problems and then we went out soon after and I tried to accelerate from about 2000rpm in 4th gear. I could feel the turbo start to boost at about 3000rpm but it felt very hesitant then the engine warning lamp started to flash! I tried the same thing a few times (accelerate from low revs under load) and the same hesitant boost and flashing warning lamp, now the lamp has stayed on constantly!
The car has got a warranty so hopefully the place I bought it from will sort it out but any help would be gratefully received as I dont want it bodging by some garage that know nothing about subarus!

Cheers, Craig