88 Columbia speed issue

[Keno-man]

I have the above cart that I have installed headlights on and removed the govenor. My cart at different times seems to run at half speed and half power until after a few minutes of driving but sometimes longer. I noticed while driving at night with the lights on, that the lights would suddenly dim slightly and the cart would take off. What would cause the cart to go faster and have more power when the lights dim.?