Engine reduced RPMs to 400 while driving and shuts off?

Thanks for your time.
Yes, every single vacuum hose I checked and renewed.
Is it okay to adjust the idling?
When I start the car and start driving.
No problem at all.
After driving 2 to 3 miles.
The RPMs are dropping down.

Correct me if I am wrong.
The new fuel injector might be giving this low RPMs.
Thank you again.

Hello Joe,

Thanks for your advice.
I changed Air Contro Valve and cleaned the throttle body and the shutter.
Now it stopped hesitating when stop and go.
But still shutting off after every few minutes.

Thanks for your time.
I am cleaning throttle body, shutter and renewed spark plug wires. I drove close to 85 miles without any problem when the car was in parking. It was idling close to 1,600 RPMs.
When I was driving it was not hesitating nor did it shut off.
Next morning when I started the car it started misfiring and didn't want to move, I checked the codes.
They were po120, po 505, po172, and po301.
I really don't understand I change fuel injectors spark plugs spark plug wires coil fuel filter fuel pump.
I went in manually to increase the RPMs to 1,500 and drive 4 to 5 miles. It was running okay. But, I am afraid to go for a long test drive.
Please tell me what and where I am making a mistake.
Or some type of Karma which is on my head not allowing me to do anything right.
Thank you all.