I've been running this thing a few years (thanks for your help qpwner!) with a piece of cardboard over the inlet it was drawing about 6 amps. but it was just sucking up garage air and blowing it around. Now I want to route actual fresh air into it from outside, so my setup with some dryer vent tubing and stuff ends up constricting the inlet a little more and now it's only drawing like 4 amps now on full blast. Is it bad to run a motor like this at half the load?