How do I know if the valve cover gasket/wiring harness has gone bad. I am not throwing any codes. At almost 80.00 a pop I really dont want to replace both of them. I go for a long period driving on the freeway and seems like it is missing or popping under hood. I have change filter after possibly getting bad gas. At one point a couple months ago it was loosing power and missing at low RPM's. It would run pretty good at higher RPM's. Anything would be greatly appreciated.