emission control causing rough idle?

Check for vacuum at the hose to the EGR when the engine is idling. There should be none. If there is vacuum, you will need to make sure that all of the vacuum hoses are connected properly and that the EGR is not connected directly to manifold vacuum.
You will need a FSM or at least a Chilton's or equivalent manual to verufy proper hose routing. Just going out and spending $25 on a new could prove to be a waste of money
if you don't know for sure that the valve is bad.