[falloutboy]

U may also look if there is a suitable flasher relay for 90s / 2000 GM cars for retrofitting LED signals.
If not, you have to install resistors. Its not the voltage that makes the signals flash faster, its the missing load in the circuit.
eg. 1 bulb has about 5 Watts, 1 LED may only have the equivalent of 5 Watts (meaning it burns as bright, but only draws maybe 0.5 watts) - hence your flasher relay is sensing "missing bulbs".