Ok, wait on the seafoam. It was a suggestion as I thought maybe you had bad gas in the tank. Sitting for a year without having new fuel added is a good way to stuff up the fuel pump.. and/or injectors. What were the codes you got from the scan, exactly? And now that you mentioned the coil pack, you will want to check that out. Disconnect the coil from the harness. Careful as to not break off the plastic tabs. Get an ohm meter and test the resistance of each of the coils. Set the meter to K-ohms setting. The coilpack has 3 separate coils on it. One for every 2 cylinders. Standing directly in front of your engine bay, one coil goes from front to back, NOT left to right. So, start with the first 2 cylinders on the coil, that is, the two on the coil pack on the very left side. Make sure to not mix up the wires when you put them back later. Measure the coil from the two coil sockets. The resistance should be from 9 K ohms to 15 K ohms. After measuring, plug those two back in their correct sockets and move to the next two sockets in the middle. Repeat for the middle and then the last two. If the resistance is well out of range, replace the coil pack.
Exactly how does the engine run? Does it run any different when hot....cold? Does it shake a lot or miss? Need as much info as possible.