Vibration at 1400rpm
 

I bought my 08 5at Z at 143k miles and it's been smooth sailing ever since with routine oil changes. However recently as I've crossed the 150k mark I've noticed a very slight vibration in the steering wheel, pedal, and shift knob at 1200-1400 rpms. Any higher or lower than that and it goes back to normal. I can feel it in the pedal primarily. Any idea what this could be? Doesn't make any noise just a weird vibration that definitely wasn't there before. Thanks