By tone suck I mean the life going out of the sound...sounding duller, losing any sparkle. I discovered recently though that my main issue was that I had the bypass volume for the amp block turned down - putting that back to 100% pretty much cured the issue. I hadn't realised that this value was stored separately from the activated amp block volume and is applied, even if the amp block is disabled. I wonder how many others are having the same issue without realising it :)
I think the impedance setting only applies when you have a modelled pedal with an odd impedance rating first in your chain...like a fuzz face. That can change the tone, even when the pedal is bypassed. Setting the input z to a value, rather than auto, gets around this 'feature' if its something you don't want. I think this is a case of Line 6 being too authentic for their own good!
Yeah, my settings are as you stated. It's just a side effect of running the master volume on the pod up full...makes everything loud. :)