Turn signals flashing rapidly after installing new LEDs?

There is no flasher relay on that car, the turn and hazard lights are both powered directly from the body control module. To use LEDs, you have to make the BCM think they are normal bulbs. That means either the better LED bulbs that are made to mimic a halogen or you add resistors. However, you need to be very careful to only add enough resistance that the BCM thinks they are the correct bulbs, if you add a higher amount, you risk burning out the internal driver chips in the BCM.