Here's something you can try:
Pour your juice into a clean container (not the one it came from). Wash the coil in hot water (and the rest of the tank while you are at it). Dry it out with a paper towel, and then take a hairdryer and dry the wicks. It doesn't take long, less than 5 minutes altogether. Now put it back together but leave the cap off and the silicone top of the atomizer head with the metal insert.
Dry burn it about 5-6 times for a few seconds after it glows red. This will clean off all the gunk on the coil (which may very well be black and look like one solid chunk), and improve the flavor and vapor for a few days to a week until this process should be repeated. You can scrape it a little if you have a bad chunk on there but don't move the coils, go parallel with it, not perpendicular.
While you are dry burning it check to see if the coils are touching anywhere - they will typically glow much more in that area. If that is the case then you need to take a needle or toothpick and spread those 2 apart. Be safe and take the tank off your battery first. Should you decide to leave it on and and do it, do NOT hit the battery button while you have metal on the coil. If you do then the Twist will short out and be dead forever. Alternatively, it is possible to use a toothpick and move it while you burn but it's really not necessary with a Vivi Nova since you can see the coil so well. I personally find that the smaller and sturdier your tool is the better accuracy you will have in moving a coil around.
If you want to learn how to rewick them you can maximize the performance of the Vivi Nova anyway. Full details on how to do this (with video) can be found in The Vaper's Handbook (link is in my signature). This will effectively make your question null and void because I see no reason it wouldn't solve all the problems you are having with it. The head itself is the valuable part. Coil and wick are pretty cheap. I prefer cotton or bamboo thread to silica, but they can't be dry burned - you just replace them more often (like once a week at most). The flavor is superior when using these materials, and so is the wicking properties. Many people like to use cotton candle wick. Just make sure you boil it first and never let it run dry or it will burn right through the wick. I have had silica wicks last me for a couple months or so, but there are preliminary tests that show that silica is bad for your lungs to use (that's also in the Vaper's Handbook). The choice is yours on what you want to do, but I'd try to fix what's there before you go re-wicking it. If nothing else than for the experience.