Mostly the vibration is noticeable in 3rd or higher gears @ 2500+ rpm while aggressively accelerating. When I ease up on the throttle and increase speed gradually all is smooth.
That's not terribly low RPM, so I would start the process of elimination...first the tune...if you put the stock tune back in and the vibration goes away, then I would try a different tune, and then auto tune from there.
If it does not go away with the stock tune back in, then re-flash the tune you're running and start looking at the exhaust, A/C, etc.
I'd also try and be closer to 2800 RPM or higher on WOT acceleration.