Troubleshooting stumble at idle in gear

This weekend I replaced the NGK 7-series spark plugs with hotter 5-series plugs. I also reset the distributor reluctor gap to 0.008". Of course while doing that I also disconnected and reconnected a lot of things. And while reading out voltages last night, I swapped out my ballast resistor for a new one I had in the glove box (the measured resistance was not much different between the two). After all that, the idle was much better this morning, really not bad at all. Having done so many things at once, I'm not sure what did the trick. We'll see if it lasts. Some day I will switch to HEI.