Is there any fuel dilution or excessive smoke? Turbos can consume oil through their own seals. The mechanic could have inadvertently installed piston and oil control rings incorrectly or broke one of them on install. This can absolutely happen, regardless of the skill of the mechanic or garage.
I had an 855 Cummins that I inframed that would smoked excessively on throttle tip in, but not at idle. It drove me nuts. The problem was a 3/16" plug that was not installed by me in the cylinder head. The hole is used for a positive crankcase ventilation system on naturally aspirated 855, and the later heads don't even have the hole. Since the exchange cylinder heads are fairly generic, one of them had it and I missed it. At the time I was Double Geared, meaning that I was a Master Truck Technician and Master Automobile Technician, at the time, less then 700 of us in the country.
If you pull the exhaust manifold back you should see coking in the offending cylinder exhaust ports. The fuel dilution issue could be over fueling injectors that have washed the oil film off of the cylinder wall, which will produce rapid wear and rings not sealing. The oil will also be diluted and consumed. This condition will also grow oil on the dipstick, so if it is over filled, see if it smells like diesel fuel or does not feel normal.
I hope this helps.,
Scott
