radio wiring diagram

Does anyone have a diagram for the radio wiring loom.for a 2003 Seat Ibiza, The previous owner had hacked off the ISO plugs to fit their own radio.I have a radio connected up but i have 3 wires spare and i dont know where they go?Two are the same colour Any suggesions to which pin on the iso bock they conect to. Although the radio works ok reception is very poor,someone suggested thereis a aerial amp

2 of the wires are white with a streak of purple and 1 appears to be greeny grey with a streak of either white or yellow.