TDI rough idle
 

I have a 2001 Golf TDI which has a problem of idling rough, especially when it is cold. As it warms up the rough idle will smooth out some but it never is totally smooth. It is so bad that I have to put it in neutral (it's an auto trans) when I am stopped at a traffic light. I have had a few people look at it and they don't know what it is. I recently had the injector pump rebuilt for another issue and that didn't fix it. My glow plug warning light flashses all the time and the check engine light stays on. I have changed the glow plugs & the fuel filter also. Anyone have any ideas????