If you're not testing, I REALLY hope you're at least using it on something electronic with a low ohm cut off and short protection. Even then, it's not a good idea to fly blind like that. Safety chips can fail. I mean I use a safe vape chip that I attach to my battery, but I wouldn't bet my life on in. I still use an ohm meter on the coils and a multimeter on my batteries, and I do the math.
If it's vaping better at a higher voltage, my guess is you made a coil with a much higher resistance than you were aiming for. My guess would be 3+. It might also just be a bad build. I've found that if I build a junk coil that doesn't heat up from the inside out, it doesn't work very well.
Ohm meters are cheap and very handy my friend, and pretty much every online vendor that sells rebuildables sells them.