Ford F-150 (2004-2008) :: 2005 - Check Engine Light Came On - Cylinder 5 Misfire

I have a 2005 f150 with 96,000 miles. Long story short, last August I was headed to the mountains going up a steep long hill and the engine light come on. once i was over the pass the light went off. During my 4 wheelin' trip it never came back on until I was headed home and going over another pass and then it stayed on for a couple of days. I had it checked and it was a cylinder 5 misfire. I did some research and found that replacing the coil cover might fix the problem and if not the spark plugs would need to be changed.

I changed the coil cover, problems solved... until I headed to the mountains. light came on and then eventually went off later that day. I didnt think much of it. then a few months later i was headed to the mountains again and the light came on in the same place on the steep incline hill. I. took it back to the shop, same reading. I decided it was time to replace the spark plugs anyways so I would invest. I have new plugs and everything is good however, I had no plans to go to the mountains in the near future. Now, a few months later I headed to the mountains and crossed my fingers it would not come on but it did.

I've done the research again and it seemed like the coil cover and spark plugs are usually the cause of the problem...however I have changed mine. The light is now off again. I don't understand what is triggering the problem and what is really happening and if it is safe to keep taking to the mountains with this happening. I did notice that everything was fine at 60MPH but once i hit the hill and steeped on the gas to go 65 and hit 4-5RMP that is when the check engine light came on...