The car won't run well w/o pre-cat O2 sensors, so you must mean post-cat sensors. If they are in place, the DME will report a cat poerformance problem, since the cat is gone, and not doing its job. If not in place, the DME will set a code that they are missing.
What exactly were the codes?
Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.