I changed my air filter in my altima to a Pure one filter about 3 months ago. I noticed first thing out of the box it has a coating of oil which we all know why. Any way Ive noticed that the altima is getting harder to start and sometimes stumbles at idle but I dont have a CEL. I decided to clean the MAF and noticed it had an oily coating on it. I cleaned it with MAF cleaner and now it starts and idles better than ever. Just my observation but I dont know how else my MAF would have got covered in oil. Take it or leave it.