If you install Cobra Dragster pipes on a 2005 Honda Sabre VT1100C2 will you have to rejet the carbs?

Odds are you will not have to rejet, pipes alone do not change the fuel mix sufficiently to require it, fi bikes are even better at making the transition of new pipes. if you experience excessive back fires or unpleasant pops try marbling/closing off your reed valves which feed back from your air intake box, this will cure that problem. In the end the test is performance, that can only be determined by the rider, best of luck.