If you have a 7.3L Ford or 6.5L Chevy, then your engine came with a Time Trac sensor. These devices were installed on the injection line to allow the dealer provided timing meter to have a place to pick up the injection pulse to set the injection pump timing. On the Ford IH/Navistar engines, these were located on top of the #1injector in the pickups, and on the #4 in an E series van. The 6.5 engines had them on the #1 line where it connected to the injection pump. Over the years, some people have removed these without considering the ramifications of doing so. All the injection lines need to be the same length in order to assure accurate cylinder timing on each cylinder. If the Time Trac sensor is removed, then the injection line will be too short, advancing the timing on that cylinder. This can result in a rough idle, and high EGTS. If you have lost yours, or discovered it is removed, you may want to install it to ensure your engine runs as good as it should. Note that non-OEM injection lines or other modifications may have legitimately made this part unwanted and not required.