lal Naja,
Patrick's suggestion of running the LEDs only in the rear is the simplest solution. If you want to run all LEDs then order one of these:
Metric Bike Diode Kit | Flashers & Load Resistors | Car Bulb Installation Supplies | LED Car Bulbs | Super Bright LEDs
This diode will stop the dash indicator from receiving feedback energy from the system as a result of the much lower power consumption of the LED bulbs.