2000 Vauxhall Vectra misfire cylinder 4

Engine Mechanical problem
2000 Vauxhall Vectra 4 cyl Front Wheel Drive Manual

hello I have a vectra 1.8 ecotec 2000 x reg and have an intermittent eml light, when the light comes on the engine will misfire so had diagnostic and came up misfire on cylinder 4 ive changed the plugs to no avail had new cam sensor recently ive noticed it only does this when the engine gets hot as first thing in the morning starts fine no eml light drive for 20 mins car drives great then. All of sudden eml light comes on car starts misfiring, wondering if the coil pack which sits along the plugs on this engine is breaking down when hot?