I disconnected the sensor cable from the cable that runs through the firewall to the EGT gauge. I did my work, and started the car without reinstalling the EGT sensor cable as I installed a manifold with no 1/8PT tap at this point. I started the car, and my EGT gauge needle just jumped back and forth from 18,000 to 19,500. I figured this may be normal as no sensor was connected.

I tapped the manifold, installed the 1/8PT fitting, and reinstalled the sensor. I started the car, and the EGT gauge needle now jumps back and forth between 450 and 500. I disconnected and reconnect the sensor cable, all looks good on the cable, etc as well. I am not sure what to try next. I would find it hard to believe that the senor went bad although I guess it is possible. Any feedback would be great.

 

I relocated my EGT probe from the Ex. manifold to the DP, and I had a similar experience. No matter what I did, the gauge wouldn't read correctly. I finally ordered another sensor and cable just to be sure (I figured that there was a break somewhere in the cable). Once I installed the new cable, all was back to normal. Weird, yeah -- I know.

If yours comes out better, let us know what you found.