You're tasting burnt stuff because your wick is probably burned. People think that the silica wicks that these manufacturers use are fireproof, but that's not true. I've burned through a ton of silica wicks. Not only that, but there are health issues being brought up on the ECF here that show that microscopic particles are released into your vapor and that they "never leave your lungs". Whether this is true or not is up to you decide. Me? I think better safe than sorry.
The best thing you can do is get yourself some 100% cotton wick (2.5mm for candles, at a craft store), or embroidery thread works in a pinch (get the thickest stuff they have (DMC brand, size #5) use 3-4 strands (I find 3 works better in a Viva Nova)), order some 32 or 33AWG Kanthal A-1 from ebay (temco) and rebuild your own coils the right way. The difference between cotton and silica with flavor is night and day. They only last about a week but it's so cheap and easy to rebuild that it's worth the improvement in performance and flavor. On a separate note, I prefer the Viva Nova Mini to the Kanger Protank because it comes with multiple heads that you can rebuild in advance and replace on the fly. The Protank's wick is tiny, harder to rebuild and stuff into the case, and there are many complaints about leaking. There's also an issue where the thing doesn't work without stuffing what is referred to as a "flavor wick", or a piece of standalone wick on top of the coil. This can have several effects. It can prevent gobs of burning juice from being inhaled by you (not a pleasant experience) or it can help saturate the wick and provide more flavor (thus the name). The other use is that it helps stuff the holes where your wick comes out without making the wick gigantic (and the coil longer), thus lowering the resistance of the coil, and preventing flooding. One of the main issues you will have is filling the diameter of the wick holes without over or under-doing it. Too thin? Leakage. Too thick? Dry hits as the wick is pinched off. It's a bit of trial and error, but hopefully with a few tries you'll figure out what works. It took me 2 tries, personally.
Lastly, I would recommend you lower the voltage. These devices often use Pulse Modulation to get their voltages higher than the 4.2 volts a lithium ion battery can provide. This often results in a somewhat inaccurate voltage at lower settings with cheaper devices. Don't be afraid to go low voltage. Your battery will last longer that way anyway. You'll know when you go too low because you won't really get any vapor. Find the sweet spot. That's what variable voltage (and wattage) is all about.