Not long ago I noticed when my brake pedal is pressed there was a bit of delay from when the highmount came on to when the left and right lights lit up.
Recently just did the impala 3rd brake light mod. love it btw! but now the delat is even greater guessing since the quick response of the leds. there is almost 1/2 sec delay now from when the 3rd brake light comes on before the outers.

Any thoughts-brake light switch(adjustment?) or BCM?

Not a major issue but kinda annoying.