I think the problem is fixed! This morning I reset the ECU and fired it up. As usual for a cold start on a reset ECU both sides went immediately to 5*. The hovered around 5-7* for about five minutes of driving and then went to zero at my first stop. However, after turning around and driving home both sides were behaving normally. I double-check the datalog and sure enough they were moving nearly in lock-step.
I can only assume it was the new sprocket that fixed the problem. I will disassemble the old sprocket and post some pics of the mechanism. There were a couple other things that could have fixed it, although it is unlikely... changing the oil; blowing out the passages in the oil line, cam cap, camshaft; cleaning the banjo filter (was clean anyways); redoing the timing belt; cleaning all the ground locations; etc. However I'm going to stick with thinking it was the $140 sprocket.
Like a dope I didn't mark the pressure plate to the flywheel. The new clutch only had 900 miles on it, it should wear in to the new orientation, right?