Okay, yesterday when I was going to work I was accelerating and my lights would dim. Then when I let off on the gas the lights returned to normal, it did this first thru fourth but not fifth. Any ideas?

2000 svt #2103 of 2150 AEM short ram, B&M short shifter, no resonator 18" Enkei RS7's, 30% tint, C-27 front bumper