I just got done installing a Custom Dash panel in my '91 RS along with using Autometer Phantom II gauges. I purchased classic dash wire harness for this model year car as well. Everything went great and was installed according to the Custom Dash wire harness instructions along with the Autometer instructions. Everything works great but the speedo. The speedo does read and it appears to read correctly, However it doesn't hold steady. It will hold a speed for a short time then start bouncing around and shooting up and down then will go back to the correct speed for 5 seconds or so then start doing it all over for a few seconds then level back off. I've pulled the dash out and rechecked all my wires per the install instructions. Everything appears good. I even regrounded thinking maybe it had a bad ground but it still does this. Could this be a bad gauge or a wiring issue? Any help I'd appreciate as I'm lost and neither place opens until Monday and I'd like to have this finished today....