What a difference!  No more stumbling at idle! One of the exhaust valve shims needed to be changed, so I finally ordered one up and popped it in today.  It's hard to believe how much smoother she runs now, although, to be honest, I was stooopid and only ordered the next size down (2.75)... I should have ordered the 2.70 as well, because I'm probably right around 0.03.  I'll order the 2.70 soon and probably change it when I get to my next check.

I am getting pretty good at opening up the valve cover, too.

Cheers!

Yup.  If the valves are tight the engine will idle poorly, spit, backfire, and/or have less power than it should.