Originally Posted by Mulder
It's definitely the LED bulbs. Their current draw is way less than the original bulbs so it causes the high blink rate, same as if a bulb is burned out. There are two solutions- one, add huge resistors in parallel to each LED bulb to normalize the current, two, get an electronic blinker module that doesn't depend on current for its flash rate.
Adding resistors in PARALLEL actually increases the current, I think you meant in SERIES.