I have a 1996 XJS

Still trying to diagnose an idle issue.

I hooked it up to a scan tool and the Short Term Trim on both banks 1 and 2 at idle, in Park, is at 24.22

When the car stumbles, this number drops to something in the 3.xx range, but only momentarily and then returns to 24.22

This is not normal, is it?

Long terms have been reset so they are at 0 currently.

Idle in Drive is pegged at 672rpm and then burps between 704 and 448rpm.
Idle in Park is pegged at 544rpm and moves between 512 and 576rpm
Engine Coolant Temperature ia steady at 188.6F and Air Intake Temp is steady at 138.2F with occasional up/downticks. Nothing out of the ordinary.