O2 CEL code issue for I30 1998

[zul8tr]

Keep getting CEL blink code 0413 (Scan tool code P0153) upstream O2 circuit slow response fault left bank. I checked the on off blinks with engine at 2000 and get 6 cycles in 10 sec for both left and right bank O2's. Also checked voltage range and get 0.1volts low to 0.7 to 0.8 volts high. Heater circuit reads 3.9 ohms when cold. All this is in spec. Once code is cleared it takes about 20 starts to set it again but only on a hot restart. What can be the issue and what to check next before replacing O2? I also have checked the connectors and both are clean and in good shape.

[elwesso]

If the o2 sensor hasn't been replaced since the car was new, you're probably just best to replace both. Seems like 60-100k is about all that those o2 sensors last.