Hi Mid Drift, if you are getting a burnt taste then the carto tank isnt supplying enough juice fast enough.... if you take out the drip tip and the carto is nice and wet when this happens then it could be that you are trying to run the carto at too high a voltage. you could also try using a thinner juice or enlarging the hole in the carto so allow more juice in
wiggle the top of the carto tank and if a load of bubbles come from the carto then i would imagine you need a slightly larger hole in it
if the carto draw feels stiff check if the battery connector doesnt have juice in it
you can also insert a straightened paper clip up the hole in the battery connector of the carto or blow any excess juice out of the carto through the mouth piece while covering the battery end with a tissue