1989 Chevy Silverado Running Problem

Were there any applicable trouble codes before you replaced anything? Did you check sensor wiring circuits? Do you have good vacuum at idle? If you unplug the map sensor, the computer will use a default value and use the signal from the tps to help with fuel. The map and tps share ref voltage circuit.

In the diagram, you can see the circuit for ref voltage. Take the connector loose from map sensor, turn the key on, no need to start. Use a digital multimeter check for around 5 volts. You can check ground also, I use a simple L.E.D., like you get from radioshack. You'll probable need to use a resistor with the led, some leds can't handle more than a volt and 1/2. One end goes to battery voltage, the other end goes to ground terminal at the map connector, connector unpluged, if the ground is good, the lite comes on.

With the engine running, do you have vacuum at the map sensor, feel.