help replaced a bad egr valve in my 2002 ford taurus. now running worse.

What is your question?

I had a coworker replace my egr valve a couple months ago. It has been running rough ever since. It almost stops running and literally shakes the car at idle. It runs great and has all the power I need except at idle. Is the valve bad? Did he put it in wrong (looks right to me)? Or did I purchase the wrong valve( yeah it is possible)? Plus it seems to be using a bit more fuel and the other night I smelled gas like when the other one was in the car.