2007 X, all plugs and wires changed, throttle body cleaned, that gas tank fluid added (all from mechanic), and I still idle at around 600-650. Its not a rough idle, very smooth, but so low that the truck reverberates and rumbles loud in the cabin. GRANTED, I haven't used up the full tank of gas with the additive (only maybe a few miles) but ive read so many places that the throttle body is the culprit.
IS there any way of adjusting the idle?

Sounds like you are waiting for the additive to clean the throttle body.

If you need to you can adjust the idle.