Flasher Speed

When the left turn signal is on and I depress the brake the flasher speeds up? Let off the brake and flasher returns to normal speed. Only happens when the left signal is on. I have checked to see if there are any bulbs out. Any ideas? Thanks

I also just noticed that the 3rd brake light is alos blinking with the left turn signal. I remove the bulbs from it and everything works normally. I'm sure the 3rd brake light is a addon from the customizing place.

There is a short or high resistive load in the third brake light. A bigger load on the flasher relay causes it to flash faster. Remove the bulbs one by one and see if it is one particular bulb. It could also be in the wiring since it only happens on the left side.