Life after OVP replacement - still idling low

My '93 300E 2.8 with 107k miles on it has gotten all filter replacements, air, oil, & fuel within the last 3 weeks, plus a bottle of Techron for the gas and an oil change. It's also finally gotten the OVP replacement it's been begging for since I bought it a few weeks ago. Finally, no more using the gas pedal to start a warm fuel injected automobile. Ahhhhh.

However, I'm still idling between 500-600 RPM. And if I try real hard, putting around in circles in a parking lot, or cruising real slow through a parking lot with the A/C on, I can still make it stall occasionally due to the low idle. (good news is that it starts right back up without the gas pedal!)

I'm wondering what my next strategy should be - chase down the traditionals of plugs, plug wires, and ??? - or should I be tracking another suspect electrical part, like the EHA or idle control valve?

Any thoughts would be much appreciated.