My experience with flavors--each made the ejuice taste slightly different:
In a cartomizer, 2.4 ohm (measured), my ejuice tastes best at 3.8 volt
In a Phoenix, with 2.4 ohm coil, same ejuice tastes best at 3.3 volt.
A different LR atomizer (don't remember ohms), 3 volt seemed to be the spot--same ejuice.
Seeing mention of 'extra flavor' is giving me an idea...order with extra flavor, and taste a few drops. Then try again, with 2 drops ejuice, 1 of plain VG (6 oz for $4 at Walmart) or PG, and taste this way. Try with different amounts of ejuice/VG/PG. The extra flavor will compensate for the dillution, and give me a chance to try different PG/VG combinations, so I'd know which mix to order next time.