Trying to get my factory tach working in my 86 gt. Pin 10 on the gm ecu to the green yellow on the cluster, wire 12. I have changed my pulses from 2,3,4,6,8 in the tune high and low. I have added a 1k 1/4 watt pull up resistor and tried the same values. What am I doing wrong? The needle jumps slightly when you turn the key to run and then when you turn the key off.