From what everyone's told me it's just how the Magnusons are designed, to be quieter and more like a sleeper. But I'm sure if you ran an open air box the sound would probably be a little louder. I think the 2650s tend to be louder than the 2300s in general as well. Talking blower whine of course.
Also a smaller pulley should make it louder, the faster it spins and more air it sucks in the louder it will be.
Also a smaller pulley should make it louder, the faster it spins and more air it sucks in the louder it will be.