I DIY, but I also use the FA flavors to just tweak a bit. For example, Shade is a great base flavor, and responds well to the addition of a bit of latakia or black pepper. I do this quite a lot actually, as it makes for a nice variation without having to have a lot of juice on hand. Shade with perique and latakia, or Mellow Sunset with a bit of clove or menthol. A few drops into a 3ml bottle before you fill it with your juice, and shake it up.
As soon as my latest order gets here, I'll be making up some great stuff, using pre-mixed Virginia and Liquid Amber, plus a splash of perique and latakia. I lost the piece of paper where I had that written down, but IIRC it's about 2ml Virginia, 1ml Liquid amber, 2 drops perique, and 2 drops latakia. Might have been double on the amount of perique and latakia -- of course, if I get either of those stronger than before, I'll still like it

I hit on this while trying to figure out what the Liquid Amber reminded me of. I won't say it's like yenidje, but once I figured out that it reminded me of some sort of oriental pipe tobacco, I was quick to use it that way. Of course, this time I'll be making a lot more than 3ml of it.
