any turbo boffs around?

i'm looking at a calibra 4x4. under full boost you can hear quite a loud howling sound through the exhaust. its quite different from the normal induction roar and exhaust noise. the owner tells me that its just because of the exhaust being a full powerflow system, the normal turbo whine/whistle is not muffled. i've driven a couple of mitsi evos and not noticed this level of sound before. it is only apparent on hard acceleration, full boost.
there is no smoke coming out and it runs very quietly under all other circumstances. i am just concerned it may be a sign of an air leak which would be not so bad, or wear in the turbo bearings which would be more bad.
btw apart from the zorst, the car is standard. standard air box, no raise in boost pressure.
any ideas?

[BigFootIsBlurry]

Turbo/exhaust/manifold gaskets? My 200 sx used to make a similar noise on full boost when they were on their way out.

Pretty hard to say what this could be without hearing it to be honest,but if the noise is coming from the tailpipe then it could just be turbo noise coz of the performance system,less baffles in it will amplify the noise,but then it could be something else,if any of the impellor vanes are damaged this could also make strange noises,does the car perform ok? maybe get it on a rolling road,well worth spending the money,can show up many potential problems


Ade