Originally Posted by tabetha

Does not sound like it has been well treated!!
It may be the turbo is knackered or the whole engine, unfortunately, I would certainly as said look at the turbo first, just see if it spins both ends.
It could be that someone has seriously let the boost off with the actuator rod, maybe to disguise a well worn engine, I hope not, but a compression test might not go amiss either.
tabetha