Hi, my 2004 Chevy aveo is misfiring. You can feel the "clunk" when it misses. Ive replaced the plugs with ngk gpower platinum alloy plugs and new duralast wires. I also recently changed my valve cover gasket due to the oil leaks. Is there any low tech way to diagnose my coil pack? Could the coil pack be going bad or is it something more?