首先，比较倾向于把现在分词短语wanting more next time解释为主语补足语。

《牛津高阶英语词典》对leave的解释如下：

[transitive] to make or allow somebody/something to remain in a particular condition, place, etc.

leave somebody/something doing something

1) Don't leave her waiting outside in the rain.

2) We were left feeling rather disappointed.

所以，根据释义，这里主动语态形式的leave sb doing (sth)可以理解为leave的使役用法，现在分词短语解释为宾语补足语。

而高考题原句中的主语I，由主动语态leave me wanting more next time中的使役宾语me，转换为被动语态l am left wanting more next time中的受动主语，进而，可以把主动语态中充当宾语补足语成分的wanting more next time解释为被动语态中的主语补足语。如果把wanting more next time解释为状语，虽然从结构形式上看，与主语l构成逻辑上的主谓关系，符合非限定动词的依附原则，但是，从语意上解释，谓语动词am always left则语意不明。