Incomplete argumentation frameworks (IAFs) are abstract argumentation frameworks that encode qualitative uncertainty by distinguishing between certain and uncertain arguments and attacks. In a completion of an IAF, each uncertain argument or attack is either added (made certain) or removed. Given a completion, the acceptability of an argument is determined by its justification status. For arguments in an IAF that do not have the same justification status in each completion, it is interesting to study which uncertain arguments and attacks are relevant, in the sense that adding or removing them can lead to a different justification status. We propose algorithms based on Answer Set Programming for enumerating relevant arguments and attacks under grounded and complete semantics.