I personally know exactly what kit taste is, as I am quite sensitive to it. I have no idea what causes it, but I have found ways of eliminating it.
1 - I find the longer you bulk age, the more the kit taste disappears. I find 12 months minimum does the trick.
2 - Skipping the addition of Sorbate helps for some reason.
3 - The more concentrated the juice, the more "kit taste" there seems to be. However, since I started bulk aging all my reds a minimum of 12 months, and all my whites a minimum of 6 months, I haven't encountered any KT regardless of how concentrated the juice is (as little as 10L all the way to 18L kits).
Having said that, here are my favourite WE kits so far. I have done over 25 kits since I started 2 years ago.
1. WE Selection international Tempranillo w/grapeskins - Discontinued
2. LE 15 Barbera
3. WE Selection Chilean Malbec