Page down to near the bottom of the list of "DGB-Mitglieder unter den Abgeordneten der SPD-Fraktion" and you will find: "Müntefering, Franz IG Metall"
But him being a member doesn't really make him or the SPD a puppet of union interests, or shows that the IGM and the SPD are closely coordinating their politics.
Examples:
http://www.friedenskooperative.de/themen/deeska59.htm
Search for Müntefering or Schroeder.
There are close relations to the SPD and as your link showed me, the majority of the SPD are members of Unions (though not necessarily of the IGM). But the German Unions are still strong enough to have an agenda of their own, which is generally far left of the SPD's agenda. And as I also pointed out in the post before, the Unions and the SPD had several arguments during the Schroeder period, mostly because the SPD is trying to evolve into a 'New Left' party to draw more support from other groups in the german society.
And the list in itself only critizized investment groups. It was the IGM cover that helped delegitimate the critizizm as antiamerican and antisemitic (because many of the listed big investment groups are owned by Jews, it seems). I just read that on wikipedia [http://de.wikipedia.org/wiki/Heuschrecken_(Politik)]. I have to admit that I didn't follow the debate too closely at that time because I felt that it was just another case of politicians blaming their inability to adapt to a changing market on economic evolution itself.