ok...
the last time i dealt with an engine that did what you are describing and was not coding out i had to replace the throttle body.

Even when i ran diagnozer on it the accelerator sensor was reading good and had full movement detection from 0 to 100%.

And even the throttle body sensor was reading as ok but when viewed in diagnozer it showed it not moving to 100% every time.

this is the only thing i can think of at this time that might cause this problem.
The fact that it is not coding a DTC code for either the accelerator pot or the throttle body sensors is really strange.

just thought of something, since you replaced all those parts did you do the 'pedal dance' and clear out any old codes that might be in the history? try doing that and see if it helps