[acshortt5]

Sounds more like the stem seals to me. Try chucking in a bottle of forte oil seal conditioner - get the genuine stuff (about £13 off ebay) and if you are running thinner oil change it to 10w40 semi synthetic and you may find that helps and will be a lot cheaper than turbo rebuild/valve stem seal replacement.

Rebuilding the turbo is fairly easy (once it's on the table in front of you...), there is a good guide on here which I followed when doing mine.