So, ever since december my truck began to misfire. Specifically the 8th cylinder. Looking at a bunch of things online, I arrived to the conclusion that it must be the plenum. Boy was I wrong. While I was saving up money to get a plenum repair kit, I decided it was about time to change my spark plugs and finally fix the valve cover gasket leaks that were going on. Well, upon removing the 8th cylinder spark plug, this is what I found: It's entirely caked in oil. No wonder it was misfiring! So, after replacing it with Champions, it ran just like the day I bought it. The moral of the story is to always keep your valve covers from leaking.