Is this thing on ???
Since my opinion dosen`t seem to count, i`ll throw this last thing out.



Raff
Since you are unsure of the trans history, a couple of things...Has the battery been dead or disconnected lately? as this will clear the learned CVI values

At a minimum, the first thing you need to do is get somebody to do a Quicklearn on it, this will reset the clutch volume indexes (CVI), if you do, have them record the before and after, On the off chance there is an internal issue this will help in diagnosis
As I said before, you can not change the idle speed, it is dictated by the PCM and even if you manage to physically open the throttle blades it will then set a "target idle not reached" DTC


Rick