[roger albert]

Hmmm,

Tough one. The obvious place (though not necessarily the correct one) to look next is the entire wiring harness including all plugs and going right up to the motronic, that connect to the TPS. It follows that the diagnostics have no way to differentiate a bad pot from a bad connection to the pot.

They should also know what the limp-home mode is for a fully failed (not just intermittent) pot. Assuming that mode runs half decently, then I'd ride around with the tps disconnected as my next step, and then observe whether the problem goes away, or changes or just what.

Moisture in GAS? (not that that should show a tps fault)

Check ground wires near motronic, injectors, and tps.

hth
roger