Collocations for dubious - adj.

be, seem, sound
become

extremely, fairly, very, etc.
highly
some highly dubious information

increasingly
a little, slightly, etc.
ethically, morally
It sounds a morally dubious proposition.

constitutionally (esp. AmE), legally, politically

Dubious is used with these nouns:
advantage, character, claim, distinction, honour, legality, merit, penalty, pleasure, privilege, proposition, relevance, reputation, tactic, taste, validity, value