Basically, I was asking if running a larger pulley would increase mileage and make the car more manageable through the foot of snow we see here at least twice a year.
I'm finding that the answer to my question is "No. Lowering boost pressure with a larger pulley won't help mpg." From what I gather, the jist of it is that even if I made Eaton M90 spin slower while the engine is using boost, it won't help much more than keeping my foot out of it.