What the hell is the "Emission Switch Maintenance Warning LamP"

I had an issue with my speedo last night on the way to a cruise. The speedo neelde was going crazy then got stuck maxed out and would bounce occasionally. I removed the cluster today what a ***** that was, but under the hood the cable is in 2 parts and in between is some sort of cutting edge 70's technology. cable goes in one end comes out the other and has a wire connected to it. Part Number is 3747025. It is a 75 dart with a 318. Can i eliminate this thing or is it necessary for the car to work. Now i also need to find the issue with the speedo.