Hi there,

In each aircraft.cfg file there is a section called 'EXITS'
in that section the location of the exits, type of the exits etc. is defined.
One of the criteria that can be changed is the speed of the default FSX jetways.
I do not remember the exact specifications but I will look it up later.
Otherwise do a google search for "FSX Aircraft.cfg Sections".
For the jetways I think it can be set to an X amount of fractions for a maximum time of 20 seconds.

Hope this helps,

Best Regards,
Marc