Excess fuel in cat converter

My experience as well. On a previous carb 308 and even on my later 355, I had issues early in the ownership with water getting in the plug wells, and it would cause a miss. Happened from washing or "horrors!" driving in the rain. The only fix was to replace the offending plug or plugs (once fouled, always fouled?). I eventually fixed the issues with water getting in the plug wells with new plug wire caps on the 308, and on the 355 it needed a new paper gasket on the valve cover plate, and replace the missing block piece where the wires enter the valve cover. I guess crazier stuff can happen, but I've never experienced a failed plug...but fouled a few.

 

That's great. Mitch.

Yep, LTFT will go up because bad plug (misfire) dumps un-burnt mixture of fuel and air into exhaust. You can explain it. I'll correct you if you're wrong.