I bought a Jetta TDI with 189K on it. It currently has 203K miles on it, after driving it for a year and love it. I hate seeing codes and started researching and working on my car. Fixing all the different pieces i find wrong. This code has been ON since I bought the car. I have done tons of research, reading forums, and video watching to help me diagnose my P0101 error code: Before we get to far into my explaining, I did swamp my cam, as I learned that it is the most common problem with this model, as the cam lobes begin to wear after so many miles. I dropped in the Stage 2 Kerma TDI cam; hoping that would solve my problem. STILL NO LUCK. I have diagnosed my car to a certain symptoms which trip the code. I clear the code. I drive for a while, and as driving down hill, the car will begin to engine break, which always throws the code. I have in the past, seen the code thrown while going up hills, but only rarely does that happen. Mainly always it happens when the engine is breaking, going down hills. I have searched for vacuums leaks, boost leaks, air intake leaks, and have found nothing that stands out. I have a EDGE cts monitor in which i monitor the MAF and MAP sensors. and while engine breaking my sensor values are not ridiculous values. I have unplugged my MAF and the engine did go to limp mode, which gives my hope that my MAF is working well. I watch values on EDGE, and it shows continous flows, rather than jump or sparatic values. So part of me does not believe it is the MAF. I will replace here soon tho, just to be sure. DOES anyone have any ideas of what this could be? My next thought is the intake manifold. When swamping the cam found that the EGR build up on the inside leaves the walls caked with black carbon. I cleaned EGR valve, but could only get so much out of the intake without ripping it off. Would that it affect the P0101 code, when Engine breaking?