1993 ford ranger stx

Okay so i'm 17 and my truck is a 1993 ford ranger 4.0 motor automatic 4x4. So recently my truck was making whistling noise but it wasn't loud like i could barely hear it, so i didn't think anything of it but now i don't hear the noise and now my truck idles rough like when i start it it just wants to stall out while idling. It will rev up and down by its self. But if i but it in gear and go down the road it will kinda bog out like loss of power but right after like 15, 25 mph it runs fine until i slow down or come to a complete stop than it will start to idle rough again. I just replaced the fuel filter and it didn't help. There's no check engine light either. So does anyone have an idea what it might be?

If it diesel if so its turbo if not its injectors but more likely turbo