Clicking noise making me crazy

[jimcuse]

I have a 2010 specialized tarmac sl3 with s works carbon crankset and chainrings, and I run dura ace 7900 cassette, RD and FD on old bontrager racelite xx carbon clinchers. I replaced the chain and the cassette and the chainrings were replaced last year. I have a clicking noise that only happens when I am in the small chainring (39 tooth) and my 19 tooth cog. It occurs only when I apply pressure not when just spinning freely. It happens while in or out of the saddle. I checked the indexing and it is right on. The chain is on the right way, I removed the pedals and relubed the threads( dura ace 7900). I regreased the DT swiss 240 hubs and the ratchets as well and the chain was recently degreased and lubed. I don't feel it is the seat post nor saddle rails as I have had this happen before and I fixed it. It sounds as if it is coming out of the bottom bracket, the chain is not rubbing on the FD nor the chain watcher. It only occurs in the 39x19 gear, when I am in the the 39x21 and 39x17- the adjoining cogs, there is no clicking whatsoever when I am applying a great amount of pressure. I would figure if it were the BB it would in all gears. Bottle cages bolts recently greased. B tension screw is set and no rub of the cog on the chain when in the stand tuning the gears. Any help would be greatly appreciated as where I live the 39 x 19 is my main climbing gear. I greased the rear drop out and the QR skewer as well. Thanks.

[painkiller]

what is the timing of the click, and was this happening with your old chain and cluster? It sounds as if it may have something to do with chainline if it does not do it on the big ring too. or your 19 cog is bad .If you access to another rear cluster you should cross check with to see if it changes anything. look closely any rubbing on any chain rivets which would go back to the timing of the click. look close to make sure no links are bent

[jimcuse]

It started to happen when I changed out the new chain and cassette but no immediately. I wonder if I put the 19 cog on the wrong way. There are the usual indentations in the freehub body from the cassettes. The clicking happens when I am pushing down on both the right and left pedals. I don't think rivets are hitting. I will flip the orientation of the 19 cog and see, there is no chain rub. I am perplexed.