Interestingly, with the A/C compressor on, the shudders become much LESS apparent. Like having a load on the engine reduces the amount of slight shaking.

I have non-resistor NGKs that I purchased from the UK, specifically because they were non-resistor replacements. I also do have new Bosch OEM plug wires. Plugs and wires are both about 12k miles / 8 months old. I did pull the plugs to look and they did look fine too, all 6 of them. I would like to rule them out now, but I do have a spare set of plugs I could try out...

EDIT: Yes, full tune up in terms of plugs / wires / distributor / cap / fuel filter / air filter / all new vac lines in the engine bay / checked for all vac leaks @ intake manifold. And several things like the airflow sensor, ICV, EHA have been replaced as well.