Valve adjust is a good idea and changing your gas is a good idea. Coils ether fail or don't their is very few cases that the coil is a little bad. Start your car up in the dark and see if you can see any spark leaking out of your plug wires. Look at your cap and rotor. Take your plugs back out you can tell what cylinder is misfiring because it will be black and possibly soaked in gas. Maybe check your fuel pressure.

What modification do you have on the car?