The Moose Truck has an air box labled "Hi Output" stamped right in the plastic under the hood. And I can't imagine you would ever need more air flow than what that gives you. In the winter, with the windows up, it's all you can do to get the door closed without blowing your ear drums out. 
I think more often than not, percieved problems with air flow are due to debris blocking the heater core, squirrel cage, or intake, or just a worn out blower motor, or high resistance wiring. Remember too, that if you upgrade your fan in some way that causes an increase in current flow, that your wiring may not be able to handle the extra load.
I think more often than not, percieved problems with air flow are due to debris blocking the heater core, squirrel cage, or intake, or just a worn out blower motor, or high resistance wiring. Remember too, that if you upgrade your fan in some way that causes an increase in current flow, that your wiring may not be able to handle the extra load.
