Thanks Dennis
I'll try that also, I've been wondering about this as my O2 sensor seemed really sensitive. using a single wire Bosch and reading on the EM2 goes from full rich to full fine with very small movement of the mixture. hope adding the earth helps as fine tuning has been difficult, so far been doing tuning more by ear, but hard to do the fine settings.
I was thinking that because I have a very short exhaust pipe from the header(no muffler) that I may have had air reaching the sensor between exhaust pulses.