How much will it reduce refinery output? What will be the economic impact?
I would expect an increase similar to that when Ultra-Low Sulfur Diesel went into effect, maybe 50¢.
How much will it reduce refinery output?
That depends how many older, less up-to-date refineries decide to spend the millions of dollars to make the changes.
Depends on the oil.
Sour oil(high sulfur content) from the Alberta tars sands will be more expensive that sweet oil(low sulfur content) like shale oil from the Bakken