The glove inflated? If so, that's a good indication that there's something wrong: the crankcase is directly vented to the compressor inlet pipe (slight vacuum) and to the intake manifold (moderate vacuum) so there shouldn't be any pressure in there at idle. The oil separator box (under the intake manifold) sometimes plug up with carbon - could be the problem right there. FCP sells the better, later style and they're cheap.
Oil in a turbo is pressure-fed, gravity-drained. High pressure oil is fed to the journal bearings and flows around both sides of the bearing, cusioning and steadying the turbine shaft. (Note: without oil pressure, the shaft feels wobbly and loose, even when brand new, though it DOES get worse with age.) On the turbine shaft, no polymer seal would stand the heat (nor would it be frictionless) so an oil slinger and a piston ring seal are used in an attempt at keeping the combustion gasses in the turbine side and the oil in the cartridge. (The compressor side includes a thrust bearing and a labyrinth seal, sometimes piston rings, but also a slinger and very occasionally a positive seal for turbos that might operate with significant vacuum on the compressor inlet). Piston ring seals have a gap, and therefore are pretty poor at sealing, so something's gotta flow somewhere... Ideally this is exhaust into the oil, which produces a frothy chocolate mixture that returns to the crankcase through a massive drain tube. It's important that the drain is large and exits above the level of the oil in the pan, because it's so frothy it takes a massive column of the stuff to push its way down into even a small amount of liquid oil, or to overcome crankcase pressure.
As you’re cruising down the highway, your engine is producing a sustained 40-60 hp and the turbo is happily doing nothing. The compressor bypass valve is open so the compressor isn’t demanding work from the turbine, and therefore the turbine isn’t creating much backpressure. It doesn’t take much crankcase pressure to overcome the turbine pressure at this point and if you’re having trouble venting the crankcase at idle, I wonder what it’s like on the highway? You MIGHT try disconnecting the vacuum hose from the compressor bypass valve and plugging it, as a trial on one highway trip – this would put load on the turbo and would increase the turbine pressure, and it might alter your oil consumption. If it does, you have a pretty good idea that you’ve got a crankcase ventilation problem.
EBR is Exhaust (to) Boost (pressure) Ratio. A good guideline for a street turbo is 2:1, meaning 2 psi exhaust backpressure for every 1 psi boost pressure. Really high horsepower cars have less than 2:1, and full out racing cars can sometimes achieve less than 1:1 and that REALLY makes power. Typical OEMs are closer to 3:1 or even higher, so that they can sell the buyer on instant torque and no lag, while sacrificing that gratifying top end. Bigger compressors also require more torque from the turbine, which means more backpressure.
The 12B compressor is smaller than the 13C which is smaller than a 15G. The 12B is paired to a TD05 turbine, which may or may not be bigger than the TD04 that the 13C is connected to. I’m pretty sure the wheel of the TD05 is larger than that of the TD04, but the nozzle area of the 04 might compensate for that. I think Mitsubishi turbos require more hands-on experience than I have because there’s a whole lot more to them than just the numbers and letters. Anyway, the 13C is a better choice than the 12B, a TD05-15G would be better yet (aside from the 90+ boltup issue), but Athal’s Garrett is a slam dunk.