misfire problems
 

Hi Guys,
I'm new here and looking for some advise on a 2006 Mazda 5 2.0l petrol sport.
I bought this car knowing it had a misfire on no4 but thought it would simply be the ignition coil.However I have now ruled out Ignition coil,spark plug and tested to power supply.
I still have a misfire on 4 and cannot figure it out.
Any help/advice would be greatly appreciated.