long-running idle/OD roughness

[Need For Steve]

How's it goin', Bonne' crew!? It's been too long!

I haven't posted much since I finished my Top End gasket job early this spring, but i've decided to really put my mind to solving my long-standing rough idle/OD shudder issue. As a couple of you guys know, i've had my share of "issues" with my car's running/idle over the last couple years, the worst of which was a bad overheating scenario early this year. After a complete top end teardown and gasket job, i've got the car running water-tight and reliable, save a constant rough idle.

The idle is the only thing the teardown didn't cure. I did not replace my plugs during the teardown simply because they all looked ok, save one which looked a bit darker than the others. The wires are new, and all 3 coil packs check out on voltage measurements. As far as i know, there isn't a reliable to way to test the ICM, but i suspect it to be the cause because...

In addition to the oh-so-slightly rough idle, I have also been experiencing constant OD shudder between ~1300-1700 RPM. Anytime the car is in OD, there is shudder until reaching around 1800 RPM engine speed. Climbing hills increases this shudder dramatically. During previous forum browsing, I've seen folks much more versed in these engines than myself suggest that a dying ICM or coil can cause a low-RPM shudder when cruising/climbing hills in OD, so I suspect it to be failing. In the vein of a real-world example, during a recent drive to band practice which involves climbing a ~20-25* hill in a 45 MPH zone, cruising at 50 MPH in OD up the hill produced such violent shudder as to slow the vehicle. The converter never unlocked, I suspect because cruise control was engaged and the computer "felt" that the car should be able to maintain speed against the load.

Could this shuddering, which i originally attributed to ignition, actually be a transmission issue?