I had fitted the NGK irridium spark plugs about 8000 miles ago and initially all was good. But recently the engine started slightly misfiring when under load. I at first thought it was a coil pack going faulty,as mine are the A revision and have been fitted to the car since new in 2006. I checked for a fault code as usually a fault code would be raised if a coil pack was faulty. Nothing showed when I scanned. So I decided to buy a new set of OE bosch spark plugs and fitted them yesterday. The difference was like night and day. The engine is silky smooth and it pulls harder through each gear. I have also noticed an increase in the mpg. I usually get 35mpg and could get 38-40mpg at a push on a motorway cruise. Yesterday travelling up to warrington I was sitting at 41 mpg nearly all the way! Lesson learnt I am not going to bother messing around with fancy plugs and am instead going to change them every 10.000 miles. The cost is £26 for a set of 4 every year, which is nothing really.

Matt

Some of them don't come correctly gapped and should be check before fitting. I blew two coil packs on my last car straight away by not checking the gap.

Are you selling them?

I checked the gaps and they were all okay. I even regapped them to 7mm as suggested on other mk 5 gti forums but still got the mis fire.