How I relace EGR valve L98 engine Engine Sevice Light tells me this is the problem.

 

remove upper plenum by undoing the bolts on the upper parts of both intake runners, unbolt the 2 7/16 screws holding the egr down, remove it. Olug the vacuum port end with your finger, then push up on the diaphragm on the underside of the valve. if it moves with your finger plugging off the port, its bad, it should hold the vacuum. If it doesnt move at all with your finger plugging it, its good. But watch out, it may move ever so slightly it will be hard to notice.

 

Thanks for helping with the EGR problem

 

Or you can get a cheap hand vac. pump and test it.