E350-4MATIC

Last year i got engine lamp on my 2010 E350 4matic. Have struggle with it since then. First i took Star diagnostic and get code p 0471 "high back pressure exhaust". Then i changed egr sensor and differential pressure sensor, same problem!! Then new diagnostic remove codes and checked dpf pressure and it was fine, so why high back pressure. When i remowe codes rengenerating comes regularly as before. I did not mentioned that the issue that engine goes in limp mode and gets noisy and power reduction. Then i start wondering what make this? When cold start, it happends and restart then everything is okay, if i use it during the day and its warm it works fine! but next day the same. Found that when ignition turn on the turbo actuator closes!! and enough to switch off and turn on its off an engine runs fine. Changed turbo actuator reset codes yesterday same ****. That p0471 is a pending code and come back. My question is why the actuator get signal from computer to close when cold? is it a temp sensor problem? I have been around forums and see that turbo actuator i a well known problem on om642.