Not to brag, but...
I stole er, borrowed this recipe from this forum weeks ago, and many people like it.
To the left of these words is my name. At the bottom is the small number 5, where my blogs are kept. Herein lies the best recipe (my opinion) for DIY coffee flavoring. To this, add the cream or other modifying flavor of your choice and mix it with your vg/pg/nic base.
Good right off, but better after some steeping (or ageing for the yankees).
Try it, you'll like it!!