HELLO. In your initial post you stated that your engine was a 307 (OLDS ENGINE maybe?). Is this what you have? Or do you have the CHEVROLET 305? Is the carb a 2bbl or a 4bbl? This info might or might not make a diffrence in the expertise within the replies you receive. When the O2 sensor went bad on my 84 CAPRICE it did not throw a code via the SES light. It just ran like it was starving for gas, good idle but on a hard/steady pull it would just lie down, cut out etc.
HOPE THIS HELPS