I agree that it sounds like a TPS, but I drove two bricks 300k miles and never had a TPS fail, which makes me not want to suspect the TPS.

What I DID have fail several times through the years was the intake manifold gasket. Multiple air leaks there will cause a surging idle, and the condition will change as the engine and manifold heat and cool at different rates, expanding and contracting.

If you have never replaced your water temperature sensor by #3 cylinder, consider doing that while the manifold is pulled back and it is easy to get at.