I search barred and nothing similar came up,
So my set up is:
AT2020 Mic, Phantom Power, Line 6 x3 Live Pod, Computer's USB

Now I'm doing softer stuff the hiss is starting to annoy me, but it only ever happens when the Pod is plugged into the USB, as soon as I unplug it it's hiss free even though the mic is still working fine.
Any advice as to how to remove the hiss and what the cause is?!

There's probably a bad ground somewhere. Or you've got interference that's being picked up by the pod.