I have been troubleshooting occasional and erratic low oil pressure and to a lesser extent low fuel pressure readings on my GRT EIS for sometime now. I finally found the problem so I wanted to share with others who might be experiencing the same issue. The fix: I moved the ground wire for the EIS FROM a stud on the engine which was shared with and on top of the ground wire for the Emag electronic ignition TO the forest of tabs ground plate that I had riveted to the firewall. This change also shortened the ground wire about 3 feet. Since this change my OP and FP have been rock solid. The manual for the EIS said to connect the EIS ground wire direct to the engine so that's what I did but little did I realize the spikes in the ground current the electronic ignition was causing.
Hope this info will save others time in their search for causes in low OP readings.
Hope this info will save others time in their search for causes in low OP readings.