im guessing the lights are LEDS as these draw less current resulting in a faster flash rate.
when i fitted an all in one tail light on my 02 the right side flashed faster too.
all you need to do change the flasher relay which is under the seat, its a two wire relay.
im not sure on the specs of the new relay, just that it plugs straight in and problem solved.
i got mine here in australia, but i think ive seen them on tobefast.com aswell.
most places who sell the aftermarket lights would sell them.
you can also get adjustable controllers too with about 12 different speed flash rates to select from.