I am also having this issue. Having owned the Pod Go for just over a year, I always struggled a bit with finding "good tone". I had better luck with high gain then I did with clean sounds (where this issue presents in a more obvious way, at least to me). After reading about this, I disconnected the pod go and connected straight to amp and my clean tone sounded fantastic. I then ran multiple tests with 2 cable and 4 cable methods, and the pod go consistently affects the tone in a way that sounds like "throwing a blanket over my amp". I love the interface, effects modeling and the accompanying software to edit patches. I am hopeful to get a repair or replacement of this pod go that functions correctly without "tone suck".
Cheers,
Jeremy