Leave the NGK coppers ...they are better than the Bosch.

The FP regulator can be checked by simply pulling off the vac hose while the car is running,...look for any fuel coming out the vac port.

The purge is most likely just gummed up..try cleaning it ..a trick is to squirt WD into the vac hose upstream and let the engine suck it thru the valve. You can tell if it is working by feeling it for a heatbeat pulse . [ approx 5 hertz]

The wet plug indicates misfire, not FP reg....test coils and if the coils are Blue labelled , those were troublesome right from the start.
Most 104 Waste Spark misfires are plug connectors under each coil...most Techs just change them when doing plugs b/c they are aware of their high fail rate from heat deterioration.
A DIYer trick is a suspect coil can be moved to see if the misfire condition follows the coil

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A Dalton