2008 Mazda MAZDASPEED3 Q&A

2008 Mazda MAZDASPEED3 Question: number 4 cylinder miss fire!

I keep getting a number 4 cylinder miss fire. I have changed the plugs and switched the coils. I still get the same problem, also I've noticed that there is oil on the number 4 cylinder spark plug treads, is this bad? I just had this motor rebuilt last year with forged internals, please help. -
Answer 1
sounds like a valve cover gasket is needed along with a boot , and the treads mean its misfiring. -