Car won't stay running

First, perform a visual inspection for vacuum leaks. Look for any loose connections. Check all hoses. Look for hard/brittle, rot, hard, soft, loose fitting hoses. PCV lines and breathers connected and leak free. In short, look for anywhere unmetered air can enter.

Don't cut corners here as a vacuum leak could easily cause the reported symptom.

Check all fuses.

Confirm that the battery cables are clean, tight, and corrosion free.

Perform the following in order.

Turn the key on but do not crank. Confirm that the theft light goes out after a 3 second "prove out". If not STOP and find out why.

Cycle the key on/pause several times (do not crank). Listen for the fuel pump to run each time. If the fuel pump does not run, STOP and find out why.

Attempt to start. Does it start and run now? If so, suspect fuel pressure leak down.

Does the check engine light come on during cranking? If so, suspect a bad CKP sensor.

Try holding the throttle half way open during cranking. Does this improve starting?

Disconnect the MAF electrical connector. Does is start and idle now?

It would be handy to know the fuel pressure.

If you are sure there's a fuel injector problem, consider an injector cleaning and flow test service such as injectorrx.com. Once cleaned and tested, they are good as new and cheaper.

A "noid" style tester would be handy to confirm fuel injector pulsing.

Will go from there based upon the test results.