Cell Formating Slows Down AutoFilter

I have an AutoFilter list of 14,000 rows by 14 columns, and the cells have some specific formating: fill color, font,
protection status, wrap, etc....

There are an additional 7 columns of formulas to the left of the filtered range.

The strange thing is----
-WITH the formating, trying to Unfilter the list takes 2 min, via a manually activated Data>Filter>ShowAll OR via a macro run of 'ActiveSheet.ShowAllData' .
(In an attempt to optimize speed, the VBA macro sets calculation to manual before the 'ActiveSheet.ShowAllData' and screen updating set to false.)

-WITHOUT the cell formating (eg. by doing Edit>Clear>Formats), the ShowAll takes about 3 sec.

Does anyone have experience or an explanation for this?

Why should the Formating affect Filtering so much?

Options for improving speed of autofilter?

I don't know if, or why it would be a factor, but note that I am using Dynamic Named Range and VBA to expand/contract the formulas

and formating to size of the list/table. Although this is not done during the filtering use.

Here is the dynamic formating code

Sub DynFmt_List()

Application. ScreenUpdating = False
With Application
.Calculation = xlManual
End With

I am wondering if some strange 'artifact' of manipulating the formating is becoming a factor?