Variable Volt devices ("VV") let you adjust the power you vape at. A regular eGo battery is usually right around 3.3 volts, to give you an idea.
The resistance of a coil is almost always at least slightly different than what it is advertised at. I think most manufacturers have a tolerance of +/- .1 ohms but I've seen many out of the box that might be even as much as half an ohm different from what they are advertised at. You can check your devices with a cheap, commonly found digital multi-meter if you think one might be off quite a bit.
The basically formula is: (volts x volts)/resistance = watts, so say if your eGo batt was putting out a steady 3.3 volts and you were using a 2.4 ohm CE5 you would end up with (3.3 x 3.3)/2.4 = 4.57 watts of power going to cooking your juice. Most people with AVP's tend to use 8 watts as a VERY approximate jumping off point for the best flavor and vapor production. The formula works in reverse too... you can find the correct voltage by taking the square root of (watts x ohms) so if you wanted to shoot for 8 watts on that same 2.4 ohm clearo you would need... 8x2.4=19.2... square root of 19.2 = 4.3 volts
Online Conversion - Ohm's Law Calculator
"Gurgly" is usually a sign of over filling. Check the top of your battery for a small pool of juice where the tank screws on and clean it up with a paper towel or something. A couple of weeks of *steady* use on a small, silica wick based device like the CE5 might mean a good cleaning is needed. I usually disassemble mine as far as I can (be careful not to loose small o-rings, etc.!) and then either wash the guts under hot water or better yet let them soak over night in a glass of cheap vodka. Dry them *thoroughly*, especially the wicks, being careful not to pull them or you might risk shorting the coil (easily fixed with a sewing needle or toothpick), maybe a quick dry burn (no juice) to make sure it's still working and you should be good to go.