What happens if I disconnect the lambda-sensor? Does the ECU switch to an open loop map? Would this map be tuned to 14,7 AFR at idle and cruise? Can the car be run like this permanently?

 

The fuel map on the stock ECU is specified in AFRs, it uses the narrowband lambda to achieve the IDCs from those figures. It wont track stoich accurately at cruise without a lambda. Alot of cars do run around with out of cal lambdas, the fuelling may walk off slightly. Best to leave it connected tbh.