just to confuse matters - tourneys nowadays tend to have some leeway thanks to the "counts as" rule.
whilst you may think this is seemingly contradictory to teh "WYSIWYG" rule it is not.
the idea is that, although you models have a particular element added to them, such as adrenal / toxin sacs, this does not have to represent adrenal / toxin sacs. BUT AS LONG AS all of your models with said "wargear" in your army count this as the same thing.
so, for instance, i "could" say that my models that i have added flesh hooks onto actually count them as having toxin sacs... but then ANY and ALL models to which i have added those hooks MUST count them as toxin sacs.