If its only #1 thats misfiring then yo ushould not need to change all of the coils. Also oil could cause problems but it should work for a little while until oil is good again. Swap the spark plug with another cylinder to make sure thats not the problem and swap the coil with another cylinder to make sure the aftermarket coil is good. If problem is still there verify you have good compression, the coil is firing as it should with a voltmeter. Then Ohm out the injector to make sure its about the same resistance as the others and verify injector circuit is working good. So if wiring to coil and injector is good, swapping doesnt change problem, compression is good, then replace the injector. This vehicle also has problems with coil 1 and 8 getting moisture in them causing problem so make sure the connectors are in good condition with no corrosion then use some dielectric greae on the connectors.
Let me know if you have questions, thanks.
P0301 Cylinder Number 1 Misfire Detected
You can barrow a compression tester from your local parts store....from what you are describing it sounds like you have a wiring problem to the coil or injector or a plugged injector. You will need to monitor voltage/ground when problem happens. Here is a picture of #1 cylinder, let me know if you have questions. Thanks