New to forum. Read lots of posts and unfortunately learned of PD cam lobe problems. 2004 Jetta TDI BEW. 140000 miles. Oil change with Castrol synthetic formulated for VW diesels at 7500 oci. p0101 code from Advance Auto generic code reader about 4 months ago. Replaced MAF. Code came back after about 500 miles. Started having intermittent black smoke and sound. From youtube video found here, sounds similar to "bupping" noise but I am confused that the noise will vary from undetectable throughout rpm range to a noise similar in video, especially at about 3500 rpm. Will pull valve cover off this weekend. Parked it until cam is checked. Is it possible to have varying levels of noise from cam wear?