Gor a misfire in cylinder 3 in my V8 merc....I'm changing all the sparkplugs as they've not been changed for 4 and a half years and 27000 miles.... (Mercedes recommend 4 years or
​​​​​45000 miles) If its an individual coil pack that's faulty should all 8 be changed at the same time or can I just change the single faulty one.....?