Did anyone figured the P0300 out? I am at 137k with my 2014 Cruze 1.4L and have already changed spark plugs at 95k with 3 new boots as they got stuck were deformed. I did install a new valve cover with bran new gasket a few months ago. It ran fine for the most part and couple days ago after high rpm it started misfiring. I cleaned the spark plugs with electronic cleaner and checked the boot coils for deformation or damage but nothing obvious. Really struggling with diagnosis here. Send help.