Chev Corsica EGR valve


I have a 1996 Chev Corsica (218Kmi) the service engine light came on. Took it AutoZone and had the code read. This indicated that there was insufficient EGR flow. Then the sale tech preceded to tell me that it might not be the EGR vale and could be a number of other sensors in the same circuit. Is that correct? Are there other sensor? I don’t want to do what other friends have done and some service centers and just change sensors until I stumble on the right one. The part is about $170 although I found one at the bone yard that I was told came out of a running motor for $50. I also asked if they could be bench tested to see if it worked and was told no. Well now that I’ve made a short story long I’m looking for advice! Thanks in advance for any and all help.