That little black thingie is the EGR backpressure transducer. It does not allow the egr to open unless there is sufficient exhaust backpressure( ie: engine is under load) they sometimes burn up. You can carefully pry the top off of it and inspect the diaphragm inside. If the diaphragm is burned then it is no good. If the diaphragm is ok you can snap it back together. Also check the hose from the bottom of the egr to the bottom of the transducer if it is damaged the transducer will not read the proper backpressure. The transducer is not available by itself, it comes with the egr valve. If it is burned it usually points to a larger problem, such as restricted exhaust. If you have a vacuum gauge, hook it to the vac. line coming to the transducer from the engine. Rev the engine a few times and you should see the vacuum signal jump up a little. If this happens the vac system is working properly. This is how we test them in the smog shop where I work. Try applying vacuum directly to the egr valve with a vacuum pump. Engine should stall. This tests the egr diaphragm as well as egr passages. Hope this helps.