I feel your pain; my strawberry & cream is a MONSTER gunker. I thought it was the heavy sweetener, since I used 2.5% when I first started making it, but now I use just .35%, and it's still a gunk monster, if not *quite* as bad as it used to be. I think it's the fact that the shisha strawberry I use is organic; there are actual strawberry solids in that stuff, even if they're so fine as to be invisible to the naked eye -- it just won't vaporize cleanly. And I use 14.5% of it, plus another 11-12% of various creams and that bit of sweetener. I'm hoping that I can keep reducing the flavoring percentages, the longer my tastebuds heal from smoking.
This juice is still my ADV, more than 2 yrs after I first started making it, but it forced me to switch entirely to RDAs within 6 months; the gunk backwash always turned the juice in the kayfun a darkening brown, and my husband said it smelled like "burnt shit." I've caught the smell of it once or twice myself, when it's badly gunked, and to me it smells somewhat like burnt plastic -- still pretty foul! But my Achilles RDA holds 2.5ml -- enough that I'm not CONSTANTLY dripping, but little enough that I don't waste so much.
Andria