I've fitted the wiring upgrade kits and it does make a difference. Previous comments are correct in that the OME wiring simply cannot carry more current and simply banging in higher wattage lamps can lead to disaster. I did some tests with different lamps (basic filament ones) and found that the increase in output wasn't noticeable. I then ran a thicker flying lead from the battery to the back of the connector and immediately you could see a jump in the brightness of the lamp. However, since then technology has moved on and there seem to be some better solutions available. I shall have to investigate those myself. But I'd still caution against just getting 'bigger bulbs' with the stock harness. Not least you won't see much difference. Worst case, you set fire to your car.