I bought 4 new BOSCH plugs for my mondy and within 100 miles it was playing up BIG time, coughing farting massive falt spots that varied all the time, worse when warmed up.
Tracked it down to the plugs, MASSIVE MASSIVE corona discharge about 1/2 long on them, two of them, other two ok, just can't beleive 50% failure rate, heard similar on these as well, found the std ford plugs to be best.
tabetha