I have a 97 Miata with 164k miles. A month ago cylinder 4 misfired but after changing spark plugs and wires the problem was fixed. Yesterday, a month later, the misfire came back but after replacing cylinder 4's spark plug the misfire continued. I then tested the compression and found that 1-3 had 100 PSI while cylinder 4 had 180 PSI. What could be the misfire and is the engine badly damaged?