A few basic ideas.

A basic divide and conquer tactic with code is to put something like this in several places:
Debug.print now & "some description"
Vary "some description" for different instances. Maybe format that Now as well.

Then you may be able to finger which line of code is slow.

This not necessarily going to even help, but it might focus your efforts to an identifiable culprit.

Also consider looking at TASKMAN or some better CPU usage tool to see if you're getting cycles.

And what LJMetzger said.