Thought i'd add to this thread rather than start a new one seeing as this is a similar issue i'm having in my 01. I'm getting misfire under load, more so when off-boost. It seems to be ok when it's cold but after a few mins of driving it will all of a sudden change into 'misfiring mode'. The car shakes quite a lot while idling once it starts misbehaving. I've changed the spark plugs and cleaned off the AFM but no luck. Guess just take everyone's advice and start looking at swapping out leads, coilpacks and the AFM?

Anyone got a spare AFM lying around that i could try testing? :O

Thanks.