Common to see breaks in the wiring harness to the tps.
The harness starts to fail, between the tbi and the firewall, from the constant movement of the engine. It screws up the readings, because of the inconsistant connection, and may not set a code.
Wiggle the harness as a test, if no change, then my advice sucks.
Also check the main harness, by the controller by the battery, common for wires to erode from battery acid. You'll have to pull out the battery to see.
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