I have a KGO.
What is the difference between a 1.7 and a 2.8? Dual Coils and Single?
I just got a tank I think... I filled it up and its a 1.7, I'm not sure that I'm doing it right because there is not a lot of vape.
Ay! The Questions!!!!!!

What is your exact set-up? What voltage are you using it at? Did you pre-fill it and let it sit for 30 minutes? Do you let it rest every 5-10 drags for a few minutes? That will mostly determine why your not getting much vapor. If you did all of that and still having problems. It's a dud.
The difference is the 1.7ohm is LR/low-resistance which is meant for lower voltages. It will give you a hotter vape at something like 3.7-4.2V. Careful since dessert/fruit flavors will probably taste burnt or not really have much flavor at all. 2.8V which can basically be considered HR/high-resistance is better suited for 4.2V to 6V. With lower voltages, you will notice that it's a very cool vape.
Anyways, DCC and single coil cartos differ in the way they utilize the power that is being given to them. Single coils do a lot better but, you have to be careful with what ohms you match with it's corresponding voltage. DCC are deceiving. Even when it's rated at 1.5 ohms. It requires more power to get an optimal vape out of them (due to two 3ohm coils).