My number 1 cylinder is missfiring. Already chnged the coil pack. Car is already at 100000 miles. Spark plugs were changed with the bosch 4+ about 40000 miles ago. Fuel filter was replaced 30000 ago. Emptied a bottle of fuel injector cleaner into a full tank of fuel and the engine light continues to light up. Can somebody shed some light on this situation; do I need to replace the fuel injectors or is there a vaccum leak of some sort.