I'm with djs and xtwo. I'm thinking those eGo-style batteries output around 3.7-ish volts, and on a Nauti, that may not be enough. If my math is decent, that's only about 7.6 watts, and like djs, I run my Nautis around 10W or more.
However, you mention going back to your dual-coil evod.... If that's been running well, I would be a touch surprised that you can't get consistency with the Nauti.
Like xtwo comments, play with the airflow - I find that I adjust occasionally to compensate - especially for where my juice level might be in the tank at the time.
The other thing is, take the Nauti off your battery, and covering the airflow hole with your mouth, blow out. You might have some juice in the chimney which is causing the gurgle. I've had that happen a couple of times, and once I clear it out, it's much better.
Also, make sure that the coil is seated well in the base, and that all your connections are snug, but not overtightened. I think I read somewhere that a user hadn't set the coil properly and he/she was getting some gurgling and even leaking issues as a result.