Replaces fuel pump, replaced fuel filter , replaces tps, replaced idle air control, replaced crankshaft sensor, still still wont run will start but when you step on the throdle it dies 1990 olds cutlass supreme 3.1

Small wonder you are confused. The possibilitiess are so complex it would require a professional mechanic to narrow the diagnosis down. Here is a very long list of what might have to be checked otherwise.

Regarding the thermostat housing, its removal could impact engine temperature regulation. Running the fan continuously helps, but the underlying issue persists.

Step by step:

Fuel Delivery Issues:
Ensure that there's sufficient fuel reaching the engine. Check the fuel pump, fuel filter, and fuel lines for any blockages or leaks.
If the fuel system is compromised, it can lead to power loss and stalling.

Ignition System Problems:
Verify the condition of ignition components: spark plugs, ignition coil, distributor, and spark plug wires.
Faulty ignition parts can cause intermittent power loss and starting issues.

Electrical Connections and Wiring:
Inspect all electrical connections related to the ignition system, including ground connections.
Loose or damaged wires can disrupt the electrical flow and affect engine performance.

Air Intake and Air Filter:
A clogged air filter restricts airflow to the engine, leading to poor performance.
Check and replace the air filter if necessary.

Throttle Position Sensor (TPS):
The TPS monitors throttle position and communicates with the engine control unit (ECU).
A malfunctioning TPS can cause power loss and stalling.

Idle Air Control Valve (IACV):
The IACV regulates idle speed. If it's faulty, the engine may stall or struggle to start.
Clean or replace the IACV as needed.

Vacuum Leaks:
Inspect vacuum hoses, gaskets, and the intake manifold for leaks.
Vacuum leaks disrupt the air-fuel mixture and affect engine performance.

Faulty Sensors:
Modern engines rely on various sensors (e.g., crankshaft position sensor, camshaft position sensor) for smooth operation.
Use an OBD-II scanner to check for error codes related to sensors.

Compression Issues:
Low compression in one or more cylinders can cause power loss and starting problems.
Perform a compression test to check cylinder pressures.

Starter Motor and Battery:
Ensure the starter motor engages properly and turns the engine over.
Test the battery voltage and connections.

Exhaust System:
A blocked or damaged exhaust system affects engine performance.
Inspect the exhaust manifold, catalytic converter, and muffler.

Engine Control Module (ECM):
If other checks don't reveal the issue, consider examining the ECM for faults.

Sound like fuel starvation, run a pressure test on the pump while running, is you see the pressure drop then you got somewhere to start at. Wonder if your gauge is not working correctly and the car is simply low on fuel. Also the fuel pressure sensor may be acting up, you will need a live data scanner for that.

check the crankshaft sensor and fuel pump pressure

Possibly the throttle position sensor. Or maybe you are having a problem with the fuel injectors. I would have the fuel pressure checked for proper pressure-that's the point of replacing the pump: proper pressure is critical for good driveability. Replacement pumps, particularly aftermarket, can sometimes not perform adequately.

The plugs and crank sensor could have done it, but the TPS and idle air control would have nothing to do with a random miss.
A more likely cause is the ignition module or a fuel problem. You may have to wait until the problem is bad enough to kill the engine or you have more codes to check out.

Tune up,plugs wires,coils.crankshaft sensor.

It's probably one of two things , a vacum leak or a bad ground.

have you checked the fuel filter

time to buy a new van.. umm what about the alternator?

sounds lie a bad fuel pump. replace your fuel filter first, if that doesnt work then you may need to drop the fuel tank to get the pump out.