carbs

While under a load my bike seems to idle a little bit rough. Also while riding there are moments where I get like a surge of power like in suddenly has all the power in the world. And then it goes away. Not quite sure what to check to correct this issue is it vacuum, spark or fuel? Maybe I need...

Looking to purchase a 2004 Carb from a Yamaha vstar 650 to put onto my 2001 Yamaha vstar 650. Does anyone know if they are compatible? I have done some research and notice a part number difference in the carb itself however the rebuilt kits say they are the same? Thank you