3.33 to 3.00 pulley = how much boost

What kind of boost increase will I see swapping the stock 3.33" blower pulley for a 3.00"? I'm seeing about 5-6 psi at 5800 with the stock stuff.

I'd say 10-12 is a good ballpark.

I saw 13#'s with the 3.00 pulley.

Would you recommend going to something like a 3.15" instead of the 3.00". This is a street car with a stock bottom end. It only has 30K miles but I would like to keep the headgaskets intact. That said, I will be adding a wideband with 42#s and likely a twEECer for fine tuning. Should I go all the way from the stock 3.33" to the 3.00"????