In the black box right beside the brake booster. It should have 5 5mm allen screws holding the cover on. Remove the cover and it is the module that has a lot of blue connectors going to it.
2004 BMW 330ci Silvergray Sport Package, Cold Package, Xenon Headlamps, Premium Package, 6 Speed Manual, Build Date 9/03
Sold - 2003 325i Sedan Japanrot 5 Speed 8k Xenon Headlamps Build Date 11/02