1999 Hyundai Accent Surging

Greetings

I bought a 99 Accent last October 07 and about 2 months later I started to get these surges where the lights would brighten and I would loose power until the surge dissipated. I would last for about 2 minutes. I've had it checked by a large chain store here in Canada three times. Done diagnostics - no problem. Had new battery, plugs, wires, and a coil replaced still have the problem. Recently had fuel pump replaced. Still have the probem. It's becoming more frequent. Any guess. I thought it might be the voltage regulator but someone on another forum said the North American models don't have one. Any answer at this point would be greatly appreciated

Thanks for your time and attention