That taste is not the juice, it is the lack of juice.
The 5v mod should be boiling away the juice at a quicker rate and the scorch is coming from a dry coil. Your juice is not wicking to the coil quick enough when you chain vape.
To wick faster, the juice has to be thinner.
I'm sure you know how to make thin juice and thick juice, so I'll leave the experiments with viscosity in your capable hands.