I think pluging vents could cause or add to a oiling problem. If the engine is building crankcase pressure the turbo cant drain back right. Dont know if thats you problem but it would be worth looking into. ANy kinda problem with the oil return line could also cause this.
The intercooler should be bone dry, but if you replaced a old turbo that was having problems you might need to clean out the pipes and cooler first. If they where known to be clean then there is a problem.
I would just go over the basics real good before calling it the turbo for sure, although it can just as easy be the turbo itself but the only way to know for sure is to know all the rest of the system is good with no restrictions. That plugging of the vent sounds like a real good place to start. Unhooking the oil return line from the engine and letting the engine idle with it loose would verify if the oil return line is restricted.
Jess
