1999 Chevy Astro idles rough, engine cuts out. When throttle position sensor is unplugged engine runs fine. I have replaced the tps, no change.

I recommend you test the tps according to procedure below. Especially step 8. Suspect you will see drop outs in the voltage, which indicate sensor is worn out.
Operation

The Throttle Position Sensor (TPS) is mounted to the side of the throttle body and connects to the throttle blade shaft. The TPS is a variable resistor that provides the PCM with an input signal (voltage). The signal represents throttle blade position. As the position of the throttle blade changes, the resistance of the TPS changes.
The PCM supplies about 5 volts of DC current to the TPS. The TPS output voltage (input signal to the PCM) represents throttle blade position. The TPS output voltage to the PCM varies from about 0.5 volt at idle to a maximum of 4.0 volts at wide open throttle. The PCM uses the TPS input, and other sensor input, to determine current engine operating conditions. The PCM also adjusts fuel injector pulse width and ignition timing based on these inputs.
Testing

In order to perform a complete test of the TPS and related circuits, you must use a DRB or equivalent scan tool, and follow the manufacturers directions. To check the Throttle Position Sensor (TPS) only, proceed with the following tests.

1. Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion.
2. The TPS can be tested using a digital ohmmeter. The center terminal of the sensor supplies the output voltage. The outer terminal with the violet/white wire is the 5-volt supply terminal and the black/light blue wire is the sensor ground terminal.
3. Connect the DVOM between the center terminal and sensor ground.
4. With the ignition key to the ON position and the engine OFF, check the output voltage at the center terminal wire of the connector.
5. Check the output voltage at idle and at Wide Open Throttle (WOT):
6. For 1996 vehicles at idle, the TPS output voltage should be greater than 0.35 volt (0.4 volt for the 2.4L engine). At WOT, the output voltage should be less than 4.5 volts (3.8 volts for the 2.4L engine).
7. For 1997 and later vehicles at idle, the TPS output voltage should be about 0.38-1.20 volts. At WOT, the output voltage should be about 3.1-4.4 volts.
8. The output voltage should gradually increase as the throttle plate moves slowly from idle to WOT.
9. If voltage measures outside these values, replace the TPS.
10. Before replacing the TPS, check for spread terminals and also inspect the PCM connections.

the problem if from the map sensor.. when you change it it will run rough and keep cutting off,, keep stating it back and reeving over and over as soon as it cuts off again keep repeating until the CPU gets calibrated with the new sensor and it starts idling smoothly..

I would recommend that you have the throttle body cleaned out, and replace the TPS (throttle position sensor) sensor.

P2176=Throttle Actuator Control System - Idle Position Not Learned
Did you use all you old sensors,or is some of them from the new engine,I would swap out the IAC sensor or check for wires not hooked up.
If it can't relearn to idle the Idle air control might be different then your old one,but its not registering with the computer

check for vacuum leak, check throttle position sensor (TPS) sensor. check EGR valve not stuck

check the throtle position sensor(TPS) that maybe the problem.

See if the idle control is working. I have a protegee that does the same thing, although the cause of mine is diffrent, it is the torque converter clutch not disengaging when stopped. Read the code, and see if there are any. Auto Zone will read it for free and give you a print out.

adjust the TPS, throttle position sensor.

First though, disconnect battery for 1/2 hour. Restart engine and drive for 15 miles while computer relearns changes you made. Will run rough for this period.

Check and clean idle air control valve
check for vacuum leaks
suspect idle air control valve

I have experienced this problem on similar vehicles. You should try and replace the coolant temp sensor. If it is not reading the correct temp to the ecm, it will not get the right fuel map. Also, the cts will not always throw a code.