Correlation, not causation. We know that stuttering severity is inversely proportional to the amount of blood flow in Broca’s Area (Desai et al. 2017) but we don’t know if that’s the cause or an effect of stuttering. I don’t know if it’s been published yet but I’ve heard from academics in the field that attempts to increase fluency by stimulating Broca’s area via transcranial magnetic stimulation haven’t shown significant results. So the short answer is no, increasing your blood pressure likely won’t make you more fluent.