The only reason to rejet is if you change the intake , by removing the stock air filters. Changing pipes does not require one to rejet, only changing how the air intake flows.
On the Vulcan, the term "Ear shave" means removing the stock airboxes on each side of the tank, and all the attatched crap. Then installing simple "pod" type filters on each carb.
These filters "breathe" better...flow more air, so to compensate you need to add more fuel...thus you need to rejet.
Changes in the exhaust do not change the fuel/air mixture, so for simply adding a new exhaust, you do not need to rejet.
If you are having issues with the bike running smoothly, it is possible the carbs are clogged up or just dirty. Cleaning them and making sure the jets that are in there already are clean should solve the problems.