GT-3 Noise Reduction - Whats up?

I play a fender strat through a Boss GT-3, into a Crate full stack. The output level on the GT-3 is on 3, my amps gain and volume is on 3-4, When I have the distortion on, I get a horrible humming feedback. It goes away when I am playing, but comes back when I stop. I tried adjusting the noise reduction in the GT-3, but it did not help. I plugged in a gate pedal, and gated the sound from my guitar. I don't want to have to use the gate since that is just one more thing that can go wrong and one more thing to set up when playing shows. Is there a gate in the GT-3 that I don't see? Or some other method of adjusting the noise reduction, anti-feedbacker, volume, ect???? Any help will be appreciated.