It could be a number of places. Can you give me the Performance(s) in question?

As Blake mentions - there are multiple ways to do something generic like modulate the pan position.

ARPs: choose the "Control/Hybrid Seq” main category and you will see a "Pan" sub-category. With a variety of ARPs that will affect pan. Use direct mode for these ARPs.

From the reference manual:

Arpeggio types (in Control/HybridSeq main categories with Filter, Expression, Pan, Modulation, Pitch Bend,
and Assign 1/2 sub categories) are programmed primarily with Control Change and Pitch Bend data. They
are used to change the tone or pitch of the sound, rather than play specific notes.
In fact, some types contain no note data at all. When using a type of this category, set the “Key Mode”
parameter to “Direct,” “Sort+Drct,” or “Thru+Drct.”
NOTE Settings related to Key Mode are set as follows.
[EDIT] -> Part Selection -> ELEMENT/OPERATOR [COMMON] -> [Arpeggio] -> [Common]

OR - you could use LFOs. Edit the part(s) you want to auto-pan with LFO, go to menu "Mod/Control" -> "Part LFO". You can see that Pan is a destination. Set the depth to something non-zero and make sure the elements you want panning have some non-zero number for the element depth ratio. Tempo sync should be ON for tempo-related panning. There's a little more to effectively use LFO (waveform, other parameters not mentioned) -- but this will point you in the right direction.

OR - you could use motion sequence. Element Pan is a supported destination and this could be tied to an MS Lane. The MS Lane sets up the timing and movement for "wiggling" (modulating) a curve of your choosing with the final destination as Element Pan. The timing of this modulation can be tempo synchronized.

OR - similar to motion sequence - you can use Superknob Automation to modulate the Element Pan as a destination.

“Auto Pan” also happens to be an Effect Type... used to great effect on Performances like the “Vintage’74” Electric Piano (Rhodes) recreation.

There is also the “Slice” Effect Type...
All Effects with “Tempo” in the name can be set to follow or reference the current bpm setting — some can subdivide the tempo into musical values like Quarter Note or dotted eighth note, or a triplet value...

In short, there are many different ways to accomplish panning within a program... even “Alternate Pan”, and “Random Pan”... if you give a particular Performance, we can help you explore it and discover which of the many possible ways it was accomplished.

Awesome! Ill have to check as I found a few new cases as I am exploring some new packs. I am having a blast building on top of some "new performances. Its really cool how different programmers approach things differently. I also find the dynamics and touch response on keys very specifically different in each pack, lots of care and attention. I have a heavy hand at times, so its nice to see different "curves" dynamics from various performance developers / players. Thx!!!

Excellent. The sound design team is truly international and the different approaches to accomplishing things is one of things that makes this synthesis fun. And, in particular, the wealth of ways to move sound in the stereo panorama is a big reason why we insist on music stores displaying the MONTAGE/MODX in full stereo -- speakers aimed at your ears! The spatial movement gives dimension which adds so much to the listening experience.

The Motion Sequencer can be used to create elaborate, evolving Pan 'phrases' that can weave the sound across the stereo panorama. A MSeq is a documentation of a parameter being changed in real time. Instead of the Note-On events that you would find in a regular MIDI Sequence or Arpeggiato Phrase, a Motion Sequence is a phrase containing controller data like CC10 (Pan) events...

Hint: the MS is similar to an FM-X "Modulator" in that, you cannot hear it alone... you can only hear the Modulator's effect on an audible signal.

When a Motion Sequence containing a series of CC10 messages is applied to the sound you are playing, that sound will animate by panning left and right according to the values 0 thru 127 (-64 ~ 0 ~ +63) in the MSeq Phrase. You can then distribute this movement to different Parts of the Performance.

Many of the Insertion Effects have a built-in Pan function. These can be set to follow specific directions... when constructing FM-X programs, often you'll find to create a stereo sound, the programmer will use two Parts-- one to create a left side the other to create a right died... from there you can create movement where they swap sides, or chase each other. The control shapes are so flexible almost anything you imagine can be done.

Have fun!