It's all about the electrics - drivability issues fixed
 

So I think I'm finally at the end of my drivability quest. Over the weekend I cleaned and tightened the whole ignition system, from coil to spark plug, and she's running MUCH better. She used to bog down, especially when cold, like she was loosing spark. Now she much more responsive, and almost fast! :D

She does still bog just a pinch when bone cold, but it only lasts a second. And, her idle is still a bit "vibraty". Engine and trans mounts have been replaced, so I'm not sure what that is.

Things I've check along the way: reference sensors, coil impedance, fuel pressure check, vacuum gauge check (looking for exhaust clogs, vacuum leaks, etc.), cleaned every connector in the engine compartment, replaced ground to engine, cleaned battery terminals (were pretty new, replaced by previous owner), replaced every fuse and cleaned the fuse box contacts. Oh, and spark plugs, cap and rotor were replaced last year (about 1000 miles ago).

Just thought I'd share my positive experience (pun intended). Clean those electrics - it doesn't cost much, and really pays off!

check you aux air valve and secondary AC valve for correct ops.

Hmm, good idea, I haven't checked the aux air valve yet. What is the secondary AC valve?

secondary air valve controls idle the same way the aux valve does but for AC load not temp.

Gotcha. Does this work as a control through the ISV (like most VWs and Audis I'm familiar with), or is it truly a second ISV solely to deal with AC load?

its actually a solenoid valve plumbed in parallel with the aux valve and wired thru the computer. see your emission sticker