I have a lot of oil residue building up around the bottom of my valve cover / CCV cover. seems too much and it burns sometimes when it hits the exhaust and smells in the cab. I have a 2012 with 35,000 miles. I have it fully deleted and routed my ccv output up to a small filter as a delete. it seems like blowby or bad valve seals or ?? How can I test for what it might be? I have the opinion that my engine should be pretty clean. Any ideas to look at would be really appreciated.