Do your turn signals flash fast? Or, do your tail lights not work correctly?
The reason for this is your cars computer thinks your bulb in burnt out. LEDs don't use much power and don't put a the current draw (LOW resistance) needed across the terminals of your tail, signal, or break light.
So how do you make the car think there are normal bulbs installed? You must fool it. This is done by using resistor chips to make the car think that a normal bulb is sucking power from it as normal.
What is required is not normal resistors, but high wattage resistors. Reisistors which are capable in handling power upto 20-50 watts. Do not even think about using little electronic resistors that are low wattage. These resistors must be large and powerful otherwise they will melt!
To fix your Turn Signal Flashing problem, all you need is 2 Resistors.
The values depend on how many led bulbs you placed on the car. If you only installed 2 of them, one in each side of the tail light for example, then you need 2 6-8ohm resistors. The wattage on these can be 20-50watts.
If you installed 4 led bulbs,2 front and 2 tail light of your car. Then you need 2 3-4 ohm resistors installed (in the front or rear, choose)
If your tail light or brake lights are not working correcttly, you may need to do the resistor mod also. This time, you may want to try a higher wattage resistor, because the brake/tail lights are on contineiosly and not flashing, and if the wattage is too low on the resistor it could melt.
Here is a diagram to follow to install your resistors: