headlight or blower motor on high creates engine surge
 

Has anyone had an issue in which when you turn your headlights on that the engine rpm drops like 2-300 rpms. I noticed that if I have my heater on high fan, warming the truck up obviously in frigid IL temps, and then go to turn on the lights, the idle surges instantly. I changed the battery and the altenator and it still does this. The engine idles fine when the lights are off and the heater is also off. weirdest thing I have seen!
I checked the grounds and ended up replacing the ground cable for the battery and cleaning the connection points. I also redid the ground on the rear crossmember for safe measure but it still spikes voltage somewhere...
This is a 1996 Blazer LS 4 door auto with 4.3