lambda sensor dont like being run without the heater connected, they are the most fragile sensor on the bike! having said that them old Bosch 4 wires arnt to bad.
on alot of race bikes its normal to put new 4.9's in every weekend!
it could be that the sensor is shot, could be that the ecu needs a hard reset.
disconnect both battery terminals and short the loom ends together for a few seconds, this will discharge the capacitors in the ecu and should clear any faults.