You are quite correct, there is no flame trap on turbo models. There is an oil separator under the intake manifold which can get dirty. At 90K miles, I doubt it, so long as you like to keep the rpms up and use synthetic.
One of the lines from the oil separator runs to the turbo intake close to the fire wall. Pull up on the smaller one and make sure it is clean. That's it.

I just changed mine at 135K and it is a 5+ hour job, not for the squeemish. The oil spearator was 50% clogged and was replaced rather than trying to clean it out with a soak in kerosene and a prayer. Car does run better, but that is subjective.

Klaus
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1995 854T and 1998 V70R