Oh, well that makes me sad. My 2 cards have 2 diff TDP.. 110% and 115%.. which i find odd..
Anyway, thanks for cudaminer, specially the December 18th update.. amazing speed boots!
If these are identical cards and hardware revisions, you could try flashing the VGA bios of the 115% card over the BIOS of the slower card. Credit for the giant speed boost goes to David Andersen. He implemented the code in such a way that I couldn't really wrap my mind around before I actually saw his code (I've tried, but couldn't picture it).