Switching the stimulus-response (S-R) mapping after practice incurs a reaction time cost assumed to reflect difficulty of overcoming previously acquired S-R associations. These associations may be stronger if acquired while experiencing target-distractor conflict due to increased Hebbian learning. Switching the S-R mapping is also thought to enhance conflict and performance monitoring. We pursued these issues using a temporal flanker task with visually presented letters as stimuli, switching the S-R mapping after a practice phase during which the frequency of conflict trials was manipulated. To explore the role of familiarity of the S-R mapping, participants either first practiced a familiar mapping (i.e., ABCD, from left to right) and switched to an unfamiliar one (i.e., BADC) or vice versa. To avoid confounds of sequences of congruency levels with repetitions of stimulus/response features and with distractor-related contingencies, letters were grouped into pairs such that trials requiring left-hand (right-hand) responses featured only A and B (C and D) as targets and distractors. Performance was better with the familiar S-R mapping, outweighing mapping switch costs when switching from BADC to ABCD. During the practice phase, conflict effects were lower when conflict was more frequent (i.e., Proportion Congruency Effect). By contrast, we found no simple differences concerning the congruency effect or the trial-to-trial modulation thereof (i.e. Congruency Sequence Effect) as a function of mapping familiarity or of (pre-switch) conflict frequency, after the mapping switch. Our results do not provide much support for conflict-related strengthening of S-R associations and enhanced monitoring after an S-R mapping rule switch.