Whare is map sensor on 95 chevy astro - 1995 Chevrolet Astro

It is on the side of the engine block above the starter.....a little square box with wires plugged into it.........

What engine ? Does it have CPI - center port fuel injection ?

some are worn but seem to still hold a vacuum ???? could you explain
Do you have a scan tool that reads engine sensor data ? Could have mass air flow sensor ! Crankshaft position sensor . Do you know how to test obd 1 engine sensors ? Test don't guess .
Buick Electrical Part 3 Automotive Computer Operation 1990 Buick ,chevy all the same .

in the air intake hose

If you did't reset the computer then the computer will not reconize the new sensor.But if you have check your fuel pressure regulator there is a good chance if you see fuel in the map sensor or in the air intake tube its the pressure regulator.

the front sensor or "sensor one " is located on the drivers side in the exhaust Y-pipe, sensor two is located near the catalytic converter

They are the sensors that are in the exhaust. I believe that there are three in this van. Depending on what engine it has. They are the only sensors in the exhaust.

there is no relay power from control panel through pressure switchs to compressor

check the throttle position sensor or tps first also map sensor.

ignition switch not lock cylinder may need to be addjusted it's on top side of steering column under dash

weak fuel pump. clugged fuel filter. fouling out plugs.