Hi use MVP 3.0 Pro and Aspire Nautilus Mini BVC smoked for 43 years and yes i would like to stop if i can. Most of my family have died from cancer before the age of 60
We will get to the bottom of this eventually.
Whoever told you to use 100% VG juice clearly doesn't know his stuff. VG is thick by nature, 100% VG in the Nautilus will give you 100% problems. It doesn't wick into the cotton well due to viscosity, so you're vaping a mixture of cotton and ceramic.
You mentioned that even with 50/50 juice you get the coughs too. Does it feel like the same king of cough as with the 100% juice? I think that it could be down to the same cause - bad wicking. You still need to take care and to do what is known as priming - the process of making sure that the coil is saturated well enough BEFORE you take the first pull. Otherwise you will burn it straight away and the bad taste and coughs may stay even if you do wick it properly after.
What is the nicotine content of the 50/50 juice? I suggest you try 1.2mg, the idea here is not to make you taste it or get your nicotine levels up, the whole point is to work out the cause of the coughs.
What wattage are you using on the MVP? It is possible to burn a coil even if the wicking is done right. Don't take puffs that are longer than 3 seconds and don't go over 15 watts.
Get a new coil, do this:
Put a droples of juice onto each hole at the side. Repeat a few times and watch is soak into the little holes as you do it. Once you can see that the juice isn't as fast as it did at the start - you are ready for next step.
Now, very carefully, put tiny ammounts of juice onto the steel mesh that is inside the coil (do not put juice in the actual hole in the centre of the mesh).
Screw the coil into the tank. Fill up. Leave it to stand in upright position for 10 minutes.
Start vaping, but don't actually turn on the device. Yes - pretend that you are vaping, inhale as if you are vaping normally. Repeat the process a few times, taking SLOW LONG drags using one of the smaller airflow holes. Leave to stand for one minute.
Turn on power on the device, set it to 7 watts and start vaping. At first do it slow, take 5 - 6 pulls on it (DON'T chain vape, take your time). Turn up the wattage to 9 watts - repeat the same thing as before. Keep doing this till you get to around 12-13 watts. This should suffice for now. Let us know if you are getting the cloughs.
There are other reasons for why peopel can cough, but i think that it is likely to bad wicking, so let's concentrate on this first.