Will i have to re-jet if i put vance & hines cruzer pipes on a stock 03 honda 750 shadow ace.thx.?

You may not have to unless you put a free flowing air cleaner on too. Once you put the new exhaust on, if the motor starts to hesitate or back fires through the carb or mufflers then yes you will have to rejet the carb. The factory carb is set lean from the factory for fuel economy. If you run too lean with a free flowing exhaust, its possible to do damage to the engine. Best of luck.