Butt was within the time and temperature limits 4 hours under 140. Should be okay because the internal was up to 170. Nolaegghead's idea of foiling and cranking the temp up should work. Just will not have a "Bark".
REMEMBER tough and "dry" pulled pork is usually under cooked, I take it off at 200 and wrap it and put in a warmed cooler to let the juices redistribute for an hour at least.