I have an allroad c5 2004 2.5tdi. I have had a couple of issues where my Mil comes on and the code indicates an egr insufficient flow error. I have cleaned the egr valve. Not that it was dirty really, and used a vacuum generator to test the diaphragm. All seems OK. The light reappeared on the way home today so that hasn't cured it. I had wondered whether the vacuum pumps deteriorate on these engines. Should I be checking it. If so what pressures make for a good or bad pump. This also had me wondering if the check valves in the vacuum connection to the servo ever fail. I need to replace mine anyway as I broke off one of the nipples where the small hose attached. I have looked at elsawin but I can't see a procedure for testing any of the vacuum system.

Any body else had similar issues?

Thanks Mike