White smoke - misfire

So having a major issue with a K12.

White smoke from exhaust - engine seems to be misfiring - loss of power all the time

I don't think it is the head gasket, as no bubbles or issues with the oil. No fluid under the spark plugs.
(Added steel seal just incase)

Was having an issue with the coil pack (changed) - spark plugs changed timing chain done

Problem seems to go after running for a while (30 minutes+) Then can come back whilst running?

(Random misfire code on reader)

Might not be related, but usually happens on wet days, or very damp, also the fuel cap gets a lot of water sitting which has started to rust, so water might be getting in?

Any thoughts or help would be brilliant

In the Land of the Finns, during winter, we add to fuel liquid chemical that chops water molecules to very small particles and they burn/boil away without causing any-kind of problems.