GTI's with twin lamps are designed to use a composite beam for main thus using BOTH dipped and main bulbs. If this doesn't happen you are left with pretty naff lights on full beam.
Single headlamp models do not have this function so turn off the main.
It is all in the wiring - I've had a peak at the Haynes book of lies and that's not any help at all so my best guess is trace the main beam trigger wire from the stalks and see where it goes. Do the same for the dipped then if all else fails then just pop a pin across from the main trigger wire to the dipped circuit at the back of the fuse box and bingo - both alight.
Single headlamp models do not have this function so turn off the main.
It is all in the wiring - I've had a peak at the Haynes book of lies and that's not any help at all so my best guess is trace the main beam trigger wire from the stalks and see where it goes. Do the same for the dipped then if all else fails then just pop a pin across from the main trigger wire to the dipped circuit at the back of the fuse box and bingo - both alight.