2008 Mercedes 320E "Boost Intermittent"
 

This car has turbo replaced and intercooler ducts checked and car ran great BUT now after about 400 miles the boost will suddenly disappear then start it later and everything works great again. No engine codes display. I just kill the engine and later restart and it runs great for about 3-days then same problem. Checked wiring, filters, all connections ....I'm lost....Any Suggestions?

Hello and welcome to the forum! I would pull the codes; although there are not any displayed, there are likely some stored codes - this should give you a definitive answer as to where the issue is coming from. I'm also attaching a link to our site's DIY tech articles on the W211 platform to assist with any issues in the future.

Mercedes-Benz E-Class W211 (2003-2009) Technical Articles - Pelican Parts