That would seem to indicate your TPS is working and being tripped when the throttle is at rest.

You said your throttle body idle stop needed adjustment. Once you start monkeying with that kind of thing you really should do a basic throttle adjustment before looking elsewhere, especially with such dramatically high revs. There are procedures described in the FAQ, but for basic adjustment you may find it better to follow these steps:
1) Open the throttle linkage end rod and remove the throttle body. If you have any doubts about the TPS switch then test with an ohmmeter connected between the centre and outer pin (one outer pin is for idle closed the other pin is for WOT full open -not used).
2) Loosen the TPS switch; back off the idle stop screw.
3) Make sure the throttle plate is centered and can close properly without binding -look through the throttle body at a light source and ensure an even ring of space around the edge when closed.
4) Hold the plate closed; advance the idle stop screw until it just touches the stop and the plate is about to start opening; advance 1/4 turn more then secure with the lock nut.
5) Adjust the TPS switch: As you know, it should click immediately as you move the throttle away from its stop (and click again on the return); start with the switch rotated fully clockwise. For a Bosch switch, turn the switch slowly counterclockwise until it clicks then lock in place. For a VDO switch, do the same thing except with a .010" feeler gauge inserted at the idle stop screw (if you don't have a suitable feeler gauge substitute two strips of medium heavy bond 24 lb. computer paper).
6) Re-mount the throttle body. Connect and adjust the linkage rod (always ensuring there is a tiny bit of slack in the gas pedal cable). For a B230FT (or B230F on a 740), insert a .10" feeler gauge at the throttle *spindle* stop tab (not the throttle set screw stop). Adjust the linkage rod so that the throttle begins to open and the TPS click is heard then adjust it back to the point where the closing click is just heard and secure the rod adjusting nuts. For a B230F on a 240 the gap is .08"; for a B234F the gap is .13" (.06" for an early-'89 production B234F automatic).
7) For an automatic, you should then re-adjust the downshift cable (next to the throttle cable) -see the FAQ.

Now the throttle body and TPS should be out of the equation for your problem. I really hope that solves your problem as the majority of high idle situations are there.

Before chasing wildly variable idle problems much further, you should carefully inspect every air intake tube and vacuum line for potential air leaks. Don't forget the vacuum line that goes to the turbo -splits on the underside at the connector are easy to miss. Also remove and flex the accordion air intake tube to check for splits.

If you have an LH 2.2 system (which I'm not sure you do in a 1990 B230FT), you would need to set the base idle with the adjusting screw on the throttle body. You need a fully warmed engine. Basically you ground a wire in the test connector to keep the IAC valve closed and then set the base idle to spec (approx 450 rpm) -see the FAQ.

If you pass all that then go through the FAQ and/or search the archives to see if you can spot your symptoms and do further testing. There are a number of things that could be giving you grief including the block temp sensor and wiring problems. If not, get back to us. I'm sure there's more I'm not thinking of.
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Dave -not to be confused with a real expert, just goofing around at this