Ryan,

Thanks for posting this...it goes to illustrating my point made on the header thread how a too small collector will (for want of a better word) "FORCE" the motor's torque to Peak at too low an RPM which acts like a cork onthe rest of the higher RPM Horsepower curve. Looks like the 3" collector peaked at 5300 where the 3 1/2 peaked up around 5900....look how much power that is.....I know the bigger ones are stepped but I'll bet 80% of the power gain was from the larger collector letting the motor keep "feeding".