8 watts is my sweet spot on the eVic, with both Boge LR cartos and Protanks. A tenth or two higher gets me into the burned taste though.. This is with 50/50 juice, where it's good to allow a minute between vapes to allow the wick to rewet itself inside the coil.
I can never pull more than 6.5 with Silica without tasting burned taste, mine is 50/50 e juice too, how are you doing 8W? With cotton wick, I can go that high but I generally stay in 7W for battery life (18350 mini mode) and because the eVic control head near the removal top ring gets wicked hot...