The difference in the 1 7/8 and 2" with forced induction is that you will see less boost with the larger headers due to less exhaust pressure. This can kinda limit power if the super charger is all that is added. If you add a bunch of other power makers then the 1 7/8 inch headers become limiting. If you are building for the future you can get the 2" and just just a smaller SC pulley to keep boost levels up until you add your other power makers...that's how I understand things at least....someone who knows more please feel free to step in
