For shits and giggles try to find a heavy duty flasher. Dunno if they make them for your car or not. HD flashers usually are needed for towing when the flasher has to run all the trailer lights also. That might make them blink more consistantly. I did the 1157 leds in a Diplomat with no problems. Blinked normal. Just an idea. LEDS have a different resistance when they are on. Same as with blubs. Best thing is to measure the current. Then add resistance to the leds if needed to match the blubs. Only thing is that will also make the leds dimmer.