The plugs bosch make for VW may be to a slightly better standard than std aftermarket ones with their name on. As they are roughly the same price I know where I will be getting a set from.
Pete, why has No. 1 got the least efficienct exhaust port ?
cant agree with this.... bosch plugs are surely bosch plugs wether you buy them from gsf or vw..no drop in quality..thats the way i see it anyways.
Yoof. do you prefer the ngks over the w5dpo's? or just in extreme tuning cases like yours? personally i cant fault the w5dpo's but then im not running masses of power.
Of course a Bosch plug is a Bosch plug, but the part you buy from your motorfactors is not necessarily exactly the same part that Bosch will supply to the vehicle manufacturers. E.g. VW W5DP0s are VAG branded.
It's not uncommon for the OEMs to really screw down their supplies on price - so it's not necessarily true either that VW W5DP0s are better than GSF ones, it's equally plausible that the opposite is true! I don't think it's something to loose any sleep over either way.
As Yoof's already said, the Bosch plugs really don't like nitrous - and we've both found the NGKs to be equally long lasting and as hardcore as the Bosch, but at a more competitive price. In addition the newer Bosch plugs are now W
R5DP0, i.e. resistor plugs. We both found this kept popping the existing supression resistor in the rotor arm - no such issue with the non-resistor NGK.
Barring some speshness in the head, I'd agree that this was possibly a dodgy plug - especially given that it was showing either a fairly lean burn or no combustion in that cylinder before. Perhaps the plug had been dropped, damaging the electrode?