[eschaider]

That OEM computer can be run in open loop or closed loop (if you have working O2 sensors). If you do not have working O2 sensors then the ECU must always operate in open loop. The learning logic, actual vs commanded AFR or lambda (whichever you use) will either not be available or will not be accurate without the presence of the O2 sensor to read exhaust oxygen.

It is to your decided advantage to use O2 sensors and even more so to use Wideband O2 sensors. The engine will operate without them but you will give up stunning tuning capabilities.