Hi Sully,
as already mentioned in the answer of this question, the execution time is not caused by the function Update() itself - it is caused by the content that has to be displayed within the function Update().
Can you please let us know more details about your dedicated application?
If your screens are containing a lot of graphical objects (e.g. with complex operations like warp or scale that is not hardware accelerated on your platform) the redrawing of the entire screen may take a certain time.
If your screens are accessing your device drivers in order to query data, the response time of the UI and the redrawing of the screens may be delayed by the underlying system.
Without knowing the details, I can just give you some rough ideas.
Is it possible to reduce the problem to a reproducieble example? Then it will be easier to support you.
Best regards,
Manfred.