In the end yes ,although the chap with the earth idea was closest. Bottom line is that when the L2 LAME installed my radio it has mucked around with the earthing circuitry. After replacing the sensor and a new guage I ran a temporary new earth line from the gauge to the engine earth and wahlah ! It behaved normally. So rather than try to solve the rubix cube that is my little aircrafts electrics, I ran another earth line permanetly for the gauge to the negative (ground) of my battery to fix the pronlemproblem