OBD Socket 2 (fuel) Code 2-3-2 means the oxygen sensor is encountering an exhaust gas mixture that is too rich or too lean at idle.

No other fault codes in socket 2 (fuel) or 6 (ignition). Repeat the procedure in both sockets and see if any new fault codes display.

You can test the oxygen sensor on the car. The FAQ has a procedure in the Electrical Sensors article (URL in a moment). You can use a cheapo electric digital multimeter to test the + VDC lead to the single black wire oxygen sensor output. You can also test for the two wire connector heater for the oxygen sensor to see if the heater is getting power.

Do NOT test the single 02 (green on my 240) wire connector on the wire harness side using a digital multimeter.

As you responded to Dave Stevens, you indicate the thottle linkage (and throttle plate) are not closing fully. If the throttle linkage is not closing, meaning it is binding, the throttle position switch (not sensor) on Bendix is not closed. When the throttle, and, in turn, the TPS switch is closed, the idle control system turns on.

throttle plate in the throttle pivots on two nylon (?) bushings. These can wear. Yet the linkage can bind from lack of lubrication at the ball joint that connects the accelerator cable spool to the throttle. You can gentle prise open the link or drip some oil. Maybe best to clean and lube with some kind of grease.

Do you hea the TPS click when you turn the throttle cable spool to close the throttle body (with engine off!).

When TPS failed on 240, the failure was internal to the TPS as the idle control remained on when you press the gas pedal. So the engine bogs and you need a light touch to get RPMs up enough to consume the fuel.

You replaced your cylinder head, so I guess we can rule out air intake manifold leaks.

I'd hope to help you fix it. Volvo Pauly is not $$$$$$$$ and some moar $$$$ like the stealerships. I dunno how what was Brentwood (now Dean Team!) Volvo and also West County Volvo are for repair service. Ain't cheapo!

Questions?
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Woo.