There is a FAQ in the 700 forum that deals with exactly what you have described.
What you describe could be the FI computer trying to limit the rpms at idle so it doesn't over rev. The control loop is rather crude and is there only to save the engine from self destroying. Something is telling the computer to rev up and it does and then cuts off things at 2000 rpm. The most obvious guess would be that the throttle position sensor (TPS) is mis-adjusted or broken. Make sure that it "clicks" just before the throttle plate closes. Also, you may want to check that the FI-unit actually sees this "click" by looking at pin 2 of the FI unit. It should be 0 Volts at idle and battery voltage when the gas pedal is depressed a bit.
The other thing to check is the engine coolant temp sensor (ECT). Look at pin 13 of the FI unit. When the engine is warm you should see 350mV. In addition, if you've disconnected the mass airflow sensor (MAF), the computer may have gone into limp-home mode permanently which will cloud the diagnostics, so you should really check and reset any error codes stored in the system before you do anything else. However, unless the Check Engine light has come on the MAF disconnect didn't trigger any code setting.
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Max..1989 244 DL 5 Spd., V15 Phase II Cam Bilstein HD, Turbo Swaybars, Poly Bushings all round, Turbo Wheels, Black leather interior, Electric mirrors, LED dash and gauge lights and now NEW ECODES with the turn signals, 1992 black 244 next project