Gas pedal vibration/buzzing & loss in power between 60-70mph

Hey guys. I was wondering if some of y’all might have some insight on a problem I’m sort of having.

I’m not sure what it is that is causing this, but my gas pedal vibrates/buzzes pretty heavily, usually between 60mph-70mph. it feels like I’m having to push the pedal almost to the floorboard to get past 70mph.

I know bigger tires cause a loss in power, and some vibrations here and there. I’m currently running 285/75/16. But I noticed this before I upgraded tires, and it feels like it’s gradually gotten worse.

Any ideas? I’ve been searching the forums and online for answers with no luck

my truck is a 2008 v6 4.0 2WD access cab with bilstein 5100’s at 2.5.