Ah, that explains it: your power limit isn't actually in effect, which is demonstrated by the card consuming up to 161W, or 107% (not 65%), performing at 3.15 sol/J. Those are expected values for a well-made 1070. I thought the 503 sol/s at 147W was a sustained figure, which it doesn't appear to be. Got my hopes up for a second there. :D