Chevy cruze LT 2012. Last night check engine light came flashing on with traction control. I had decreased power and sputtering on acceleration. Had the code read for p0300 engine misfire. Bought 4 new plugs as a starting point. Took the coil pack off to find 2 chambers with some old oil build up and one chamber with a small amount of fresh oil splatter. The intake manifold and valve cover were replaced less than 6 months ago. Could the valve cover have blown already causing this issue? My plan is to tighten the valve cover bolts, clean out the chambers (not sure how to go about this) and then change all 4 spark plugs as they have never been changed and I have 132k miles.