If your EGR does test bad there are #'s on it that relate to the valves calibration. If you are changing it with a non-o.e unit you will need to have those #'s for reference. Also the above replies are correct, the EGR valve rarely fails. Usually it fails to close(see above about cleaning) and you get a vacuum leak through the valve or it sticks shut which may give you an EGR code- I don't know if a '95 car will set an EGR code though. Depending on the emissions in your state a non-functioning EGR could cause the NOX reading to be elevated during the dyno test.

 

I have a 95 with 3.4, and I've struggled with the EGR problem for two years. First off, I'm not sure if the EGR system on the V8 is a vacuum system or not. Mine is a digital format which I think was used for two years, and then returned to a vacuum system later. I purchased a code reader when my car began throwing a code and found out it was an EGR related code. On the digital valve, there are three openings of differing sizes. Each one has it's own code. Thinking my problem was the valve, I purchased a new one and installed it. BTW, these are expensive. It didn't solve my problem. Next I had a mechanic clean out all the EGR passages and tubes, but that didn't solve my problem either. I began to notice that it was throwing codes after I began decelerating from speeds over 30...35 miles an hour. Research indicates that the PCM sends out a call to test each valve opening during deceleration. This is where the process of elimination leads me to believe the problem lies. However, I have no idea what to do about it. After I shut the engine down, the next restart shows the code erased from current memory, but stored in historical. I have read that across the country, mechanics replace the valve first, charging anywhere fro 2 to 4 hundred dollars, and not solving the problem. If I were you, I would first check if your EGR valve is digital or not. Then I would share the information I just gave you with your mechanic, and see what he thinks. If you find an answer, I'm all ears. This problem is driving me nuts!!!