Check all your fuses first. In the engine bay and under the dash. In my experience, aftermarket lights like that are never really a good idea especially when the stock 99-04 lights look so good and have a ton of bulb options.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.