I hooked up a scanner and watched the sensor profiles while driving in a 1995 Millenia. I noticed that TC OFF light comes on in the car when I go a constant speed. On the scanner, I see O2 readings stay below 0.45 and the short term fuel trim (STFT) stop responding. The ECM status soon goes into OL-Fault. Both of my pre-cat O2 sensors are new (Bosch) and 1 I've taken back because I thought it was lazy. This has not made a difference. Computer goes into fault only when going a steady speed but comes back on in closed loop (CL) as soon as press the gas. No other warning lights.

Have checked and replaced vacuum hoses. Replaced intake and valve cover gaskets. New plugs and wires. What is going on?