I would say the valve is sticking.

If so remove it and lube it (No rhym intended) it's worthwhile doing this anyway, as they are prone for 'gumming' up and then become sticky, it's worth doing this first as it's easy to do.

If not, moving onto the TPS the first thing to do is check the output, and that at closed throttle it is open circuit, if not this will cause all sorts of idle related problems.

You will be interested in Pins 17 and 11 from memory, you will have to disconnect and remove the cover from the ECU connector, aka "hairbrush/scart", then reconnect and test those pins, the voltage reading should decrease progressively and smoothly the more throttle is applied, going to around 0.5V @ WOT.

As I say look toward the valve first!

Martin