97 t-bird can't pass DEQ!!

failed three times - first time i got these codes - P0135 P0136 P0141 P0155 P0156 P0161. all are O2 sensor heater and circuit malfunctions. i took it to a local mechanic who replaced all the sensors (cost me $350). unfortunately he didn't clear the computer codes so i failed again (got like 19 codes) and got the codes cleared at meineke. so then i drove around about 100 miles to cycle the car through again and when i took it back i failed yet again! this time with the exact same six codes as the first time.
so maybe the problem isn't the oxygen sensors or something?? all the other criteria are fine except the catalyst says "unready" - could that be the problem? someone please help me pass!

also, i previously had a problem with the intake manifold and replaced it, don't know if there's an obvious connection there.

Welcome to the forum, cantino. Since all of the O2 sensors are new, it sounds like you have a wiring problem. Be sure the sensor connectors are clean and tight with no corrosion inside the connectors. You'll have to trace the wires from the sensors back to the PCU to be sure they haven't been cut or shorted out. Have your shop check the voltages at the sensors and also the resistance of the wires.