I'm running a Soma cog (new) and a KMC Z51 chain (new). I listened very closely today and there is a very subtle clicking, but its barely noticable. I'm very noise conscious on any bike and this is barely audable. Another thought? Will a 9spd chain work with a standard 3/32 track cog like the Soma? I have a bunch of KMC Z9000 9speed chains that I got on the cheap, but I chose the wider beefier 7 spd Z51. I had intended to use a SRAM PC-48 but didn't have one handy. Still the SOMA and Z51 seem to be just fine.

I think that I have a good feel for chain tension and a good ear. My young mechanic was working on a real poor SS with a less than happy chainline for one of his running mates. I could hear the chain binding while I was sitting reading in another room. I yelled, Loosen the chain a bit. I got in return. Mind your own business, I got a handle on it. You didn't want to work on it anyway! He was right, it was and is a piece.