96 Bronco w/ 351 & AT - single exhaust - 107K miles. Have trouble code P0133: O2 Circuit Slow Response (Bank 1, Sensor 1). Does this indicate a failing (old) sensor? If so, should I replace all 3 at the same time? Since the O2 sensors are so critical, are there better sensors than others? (Note: I recently had other O2-related DTCs. I replaced all the hardline vacuum hoses, air cleaner, & cleaned the MAF (as guided by excellent guidance in another post) and the code cleared up.) Thanks to all who care.