slightly rough idle - winter fuel? (1994 Q45, 180k)

[artandscience]

So it seems like my idle either goes south a bit when it getscold out (less than 60F) or we start using winter gas (Seattle).

Right now, it's about 700rpm when the engine is warm, car in park.Idle goes up about 150rpm when in gear (and gets a bit rougher).

I've done everything service wise (cleaned throttle body, MAF, MAF contacts,fuel filter, BG44k, fuel injectors tested and ok, fuel injectors cleaned, newbattery, transmission flushed and refilled with Mobil 1 transmission fluid, new air filter) in the last 5000 miles. Still a little rough.

Just enough that I feel the idle now when I didn't last summer.

The only issue unresolved is that I have 60k on the stock platinum plugs.Should I assume that that is doing it and hold off on further fixes untilI get the plugs changed?

Ideas welcome, Stefan