I'd rule out a fuel injector first by swapping it with say cylinder one and see if the misfire follows it, if it does then the injectors faulty, if it doesn't you know its ok. Then your down to coil pack or an engine issue, you can do a simple compression test by using the proper tools which should confirm a compression issue. How ever if I was you I would chuck a coil pack on it any way for 3 reasons. 1) they aren't that expensive so its not a lot of wasted money, 2) the coil pack sits right above the exhaust manifold which is why they are a common fault. 3) I have seen hundreds (probably an exaggeration)of cars with misfires on one cylinder caused by faulty packs.