After getting the front of the car up, I could see that the notches were off by about double what I said before. So much for going by "feel".

Summary: Timing WAS off by a tooth, AND the upper BS was keyed wrong.

Yeah. Not a good thing to do by feel. The balance shaft sprocket should fix the vibration and the power should be back to normal, since shifting cam timing around shifts the power up or down, but cams also have their "sweet spot".

This is the best writeup I've found on setting up balance shafts:
BalanceShafts

It's confirmed! Other than the timing belt beeing off by a tooth, I can now say for sure that the upper balancer pulley was keyed to the wrong slot EVER SINCE I'VE OWNED THE CAR! That's 2 years now. Today was the first day since ownership of the car that I was able to cruise along at 1500rpm perfectly smoothly, with no vibration and nothing ratting. I opened a thread quite a while back (that I can't find now) regarding rattles when cruising at low rpms, and what could be the cause. Well folks, this was it!

Moral of story?: Just because something was a certain way before you messed with it, that doesn't necessarily mean that it was the RIGHT way. Especially if there were any previous owners.