Sounds like you might be using too high a % on the flavoring. I know it doesn't make sense but using too much flavor ends up with lots of aroma and little to no flavor. There are a few things you can use once you get the % close that will make the flavor pop a bit, sweetener, vinegar, citric acid, tart & sour
i noticed in my Ego-c, The Green Apple i got from Americaneliquidstore.com is a pure VG and gives awesome flavor. Smells like im eating apples and taste like it. I need to replicate that flavor, and i know its gonna be almost impossible doing it with the PG. I have a DeKang Banana premade liquid that i ordered from Litecigusa.net and that taste great too. Im not sure what the mix is of the DeKang liquids.