aren't mechanicals limited to about 3.7V? it's basically just a battery, a switch, and a pretty battery housing, right? so if you've got a 1.5ohm coil, assuming resistance doesn't change too terribly much as wire temperature rises (which being a newbie i could be totally wrong about), you're still going to max out at about 3.7/1.5=2.5A. and that's really not much current at all when you're talking about FETs. is the current state of circuitry design in the e-cig market so far behind the times that a vv/vw can't even do that much current?
what ~might~ be happening here is that the MVP's battery is getting a little old and has built up some internal resistance, limiting current output. im not all up on the myriad different lithium cell technologies, but that certainly happens with every battery chemistry i do know about.