Pork butt is pretty forgiving and not at risk (like a brisket flat) of drying out. So wrapping is mostly a question of time rather than an issue of getting the best finished result.
If I have the time, I find it easier to just let the butts keep cooking at a higher temp. Below is Chris' sage advice.
With some patience and a 225-250°F cooker temperature, the pork butt will eventually move beyond the plateau and the meat temperature shall rise again. If you want to shorten the length of the stall, just kick the cooker up to 275°F. Or if you’re really getting impatient, when the pork butt reaches 165-170°F, wrap it in foil and finish it in a 300°F cooker or oven.