Cold weather miss-fire problem - 86 Crown Vic

Last winter I reported a miss-fire-under-load problem in my 86 Crown Vic with 302 V8.
Installing new plugs and wires didn't help.
Not knowing what to replace next, I kept on driving it. Just couldn't
get down on the gas much.
Now the weather has warmed up and the problem went away completely. I can floor it with no miss whatever. Smooth as silk.
Maybe I should view this as good news, but I'm really baffled now. Any ideas out there?

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