Burner removal on Thermador range?

I am trying to remove the burners so I can get the spill tray out, this so I can access the simmer controller. The venture tube. which is shaped to take a 3/4 socket, looks like it is holding down the burner base, but when I apply 20 pounds or so it does not give. I'm afaid of appying more force for fear this is the wrong way to get it off.
Anyone know how these come apart? here is a pic: http://www.appliancepartspros.com/partsearch/model.aspx?model_id#2453
The venturi is part number 126 in the picture. This is a PSRE366S.

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