[Ahem. Update: this was just wrong, because I misread the defn of POGA-C; see comment 2, thanks to TC. To avoid polluting the record, I'll delete the rest of this post, but there's an archived copy at http://www.webcitation.org/6JMTX0nGx if you like. The paper fairy has now delivered a copy of K+X to me, so I expect to post a "take 2" later this evening. Or maybe tomorrow; I might actually try reading it properly this time.]
I have a take 2 if you're interested, but its dull.
John N-G did a nice, simple treatment of this a year or so ago. I've been surprised that it hasn't received much attention, though to my knowledge he never published it formally:
[That's not quite the same "this" as we're talking about here, but it is a very nice analysis of the impact of El Nino / La Nina on temperature trend. I think I prefer it to the Foster+Rahmstorf method, because of concerns I've seen http://troyca.wordpress.com/2013/05/21/another-reconstruction-of-underl… -W]
William, Tamino describes POGA-C as holding forcings constant at 1990 levels, while constraining the Tropical East Pacific to historical temperatures, ie, the reverse of your description. You may want to double check that.
[Oh, err, that's a good point, I'd completely missed that. I had better check. It would blow something of a hole in my argument :-) -W]
That analysis actually got a lot of typically wrong-headed attention from the bozos over at WUWT. It was somewhat hilarious.