Thanks for the info Mark. With a new earth run to lambda & MAF I get correct readings at MAF & a switching Lambda. Emmissions are bang on. I've run the new earth direct to an engine earth point. Put everything back together, bolted the ecu back in place, now the dear old thing is back to square one. Still good readings on MAF but lambda isnt switching!

Would anyone have pin data for the ECU end of this? Bosch type ECU.
Tomorrows headache