G'day. The basic test for turbo seal failure is smoke after a lengthy idle period such as 15 or 20 minutes. Smoke could be caused by various things, so not really safe to assume it's the turbo.
Things to check are firstly turbo related - check turbo oil return isn't clogged up - if it is, that can cause oil to leak into exhaust or intake and get you smoke symptoms.
Check intake - is there oil through the intercooler and intake manifold?
I'm not a hands on mechanic so I'd have to suggest getting it professionally diagnosed. The things I know you'd want cleared are:
Compression test, leakdown test, turbo oil return clear, and of course turbo itself.
I had a similar problem at 250,000Km on my BK. I swapped the engine out with a low Km BL engine and when we diagnosed the original engine found there was nothing much wrong with it but the turbo oil return was clogged up causing a lot of oil burn and all through intake and intercooler. That would have been a lot quicker to resolve than swapping an engine but on the other hand I got a low Km engine good for another 250,000Km
Good luck!
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