If it's missing on just 1 cylinder, then I'd move the coil to another cylinder and see if the misfire moves. If it does move, then it has to be the coil/lead.
Random multiple misfires on all cylinders is most likely to be a blocked fuel filter. Putting a pressure gauge on the fuel rail tapping point is the check for filter issues. You need a fuel pressure of around 55 Psi all the time, or the injectors won't form the correct spray pattern, and the ECU won't be able to fuel the engine accurately.
