Matt.F (Milton Keynes)

Hi everyone my name is Matt and I own a 2003 Subaru Imprza WRX Turbo. I have owned the car for about 8 months now and I have had this problem since i got it. The problem occurs when I turn the lights, the heater and window wipers (and most of the other electrical equipment in the car) at which point the car begins to judder and hold back. So far I have put two different alternators on the car and a brand new battery. Any help would be greatly appreciated. Many Thanks Matt.F