Don't know the engine or car at all but I guess it has the long reach plug connectors (I assume it is not a diesel). First thing I would do is take them off the plugs and check for signs of damp. For good measure squirt a WD40 type product down the hole onto the plug and the same on the long reach connector.

I had a similar problem with my OH's MX5. It was over a day after the soaking and you would of thought heat would dry it out. The car nis-fired popped, banged and was dangerous to drive the misfire was so bad. I also took apart every elec. connection under the bonnet I could see and squirted WD40 on them.

Good luck