Okay so I'll replace the EGR valve. I unplugged the vacuum on a 350 that was doing the same thing - long time ago - and it completely leveled out the idle. So I tried unplugging this one and it had no affect on the idle. It makes sense though, I admit, so I'll replace it. Just one last question. If it wasn't the EGR, what would be your very next guess? Just one and I'll accept the answer. I'm just not excited about the prospect of going in search of a vacuum leak. Ugh.