Not long ago it's had all new gaskets etc, but over the last month it's started tapping and gained a misfire on idle and whilst driving. Changed all plugs, leads dizzy etc, but still has the misfire.

Nipped off the rocker cover today for a quick look and noticed that the inlet lifter over number 4 is really soft, and the rocker arm above it is quite lose being able to turn it and lift it by hand. Turned it over by hand and it doesn't change.

Would a dodgy/worn lifter cause a misfire atall? Or just the tapping?
The head was meant to be good when fitted and was quiet for months before this.