Last year I had installed a Proform standalone shift light and about six weeks ago I installed a new Holley TBI and Autometer 2 5/8 tach. I started retuning the car for the bigger injectors and didn’t have any real notice able problems at part throttle. A month ago I got dyno time to tune full throttle, but the car would start missing round 4500-4800 RPM’s. One person thought it was a fuel problem another thought it was the coil. In hunting for the fix I replaced the coil, ignition module, plug wires and the fuel pump (the pump failed). Saturday, I was running our of ideas (short of replacing the distributor or the plugs with only 5000 miles), but I tried disconnecting the signal wire for the tachs and the car ran fine, reconnected it and it started missing again. I removed the Autometer leaving the shift light and I continued to run fine.

I thought I would post this since I had done several searches and never found this scenario.