Rust on those plugs shouldnt be there so double check AA's advice

But what i would do......is change em anyway then see if the missfire goes away before any water gets in there again.
If still there....then i would go with TB's and Marks advice......coil pack

Both my Veccies have coil packs as well......and they managed about 100k before needing replacing.
One used to make the car miss quite a bit....the other one just gives a cough at 1500rpm underload.....more than 2k and underload and its fine.
My omega misses on petrol and lpg when cold low down the revs also......worse on lpg....i know it isnt the plugs or airfilter causing it.....so i suspect its the coil pack on that too...

In fact its been getting worse.....so much that it normally puts the EML on for a bit when it switches to lpg.....but doesnt record any missfires detected.
Whats the mileage on your 2.2?.....Getting towards 100k? Coil pack
