ride_red75:
The technical explanation to your problem is that the inner workings of your thermal flasher relay depend on the current drawn by the flasher bulbs, i.e. they use the current that lights your flashers to operate the relay itself. If you change that current by installing less power-hungry LED flashers you will also affect the performance of the relay.
Old fashioned flashers typically have 21 watt bulbs while your LED flashers probably draw around 1,5-2 watts each. Thats a factor of more than ten and it will have a huge effect on the flashing frequency...as you've noticed.
I did exactly what Hail suggested; ordered the CustomLED relay. It took me all of 30 seconds to install (under the passenger seat if I remember correctly) and works with any combination of lamps whether they are 21 watt hot filament or LEDs.
Plan B, which is to install a couple of resistors in parallel with the flashers in order to mimick the old 21 watt load, is NOT something I would recommend. I can see no benefits. It takes more time, costs the same, involves messy wiring and the resistors generate heat that has the potential to damage nearby plastic or wiring insulation.
Greetings from a rainy Oslo,
Einar