Please explain how wattage and voltage can cause a reaction such as the OP?...Not to be sarcastic, I really have no clue how, other than heat, could be a causation. And if it is heat related how it could not affect the mouth yet affect the lungs and bronchial tubes...Please enlighten me!
If the Ohms of an Atomizer doesn't change, then Volts and Watts are Tied together via Ohms Law.
More Volts = More Watts. Less Volts = Less Watts.
What a MVP (or any VW device) does when in Watt Mode is Measure the Ohms of the Atomizer, do some Quick Math, and then it sets the Voltage to what will Achieve the Watts that the User has set the Device to.
The Advantage to this is if you Switch Ohms a lot because you switch from Tank to Clearo to Carto to RBA a lot, the device can make the Adjustments for you so Theoretically all the Hits Should be about the same. No Matter what Ohms your Using.
For the OP, something sounded wrong. Because He/She mention that the MVP "P" button was set to 6.5.
If the "P" means Power, and since Watts is a Measure of Power, 6.5 Watts doesn't sound like a Very Hot or Harsh Hit. If it is 6.5 Volts, then Yeah, that's gonna be Smoking Hot.
Because Watts = (Volts x Volts)/Ohms.
Then the OP said that their Tank was 1.8 Ohms. And it worked fine on there eGo.
A Non-VV eGo has a Fixed Voltage of about 3.9 Volts. So the Watts that the OP finds works for That tank is...
(3.9 x 3.9) / 1.8 = 8.45 Watts
So if the MVP is set to 6.5 Watts, and it is in Watt Mode, the Hit should have Tasted kinda Weak. Because the MVP is set to Less that His/Her eGo.
But it Didn't. It Tasted Burnt.
So that is why I told the OP to try turning the 6.5 Down until it worked. And He/She did and found that 3.3 seemed OK.
Ok so Maybe the 6.5 was Volts. And not Watts.
It's just hard to Know what is Going on When I don't have one in my Hands. Or what the Menus look like.