I've had silica wick type clearos in the past that just tasted nasty right from the start, and no amount of fixing would smooth it out. Early Vision Extermes were noted for it, and I've had it happen with CE2s as well. Generally, I found that it was one of two things. Manufacturing residue being present in the unit, or the coil being wrapped too tight and choking the wick. To remedy the first, it's why many CE2 users take everything apart, and rinse out and dry burn it before filling it and vaping it the first time. For the second, sometimes you can use a small pin and adjust the coils by using a small pin and spread them out and loosen them up a tad. But usually, once a wick is burnt, it's burnt, and there's no un burning it.