Lately my Chevy truck hasn't had as much power as it used to and seems like it's running on like 6 cylinders or something so I thought that it's either the fuel filter, fuel injectors, plugs and wires or something of that sort. Well it isn't plugs and wires (chevy dealership said they will last 100,000 miles on this truck). Well I changed the fuel filter today and that didn't seem to help worth a damn. Later on today after driving it for a bit it will start making a noise like a winding or buzzing noise inside when you rev it up or eccelerate (like how sometimes you can put the AM radio on and it will do that sometimes). Anyways does anyone know why it's doing this? I heard that sometimes it could be your PCV valve but I can't remember where that's at and what that does again.
Any help on what my power problem is and what that noise is would be greatly appreciated.
I don't know why it started that noise all of a sudden and just now I just realized that it starting doing it after I got this fuel filter in....

Thanks for any help.