I don't know any in Seremban, but if Cheras is not too far from you, you can try BM World at Bandar Tun Razak, 016 2206687 Ah Wai - BM World. They are efficient and knowledgeable. What BMW by the way?
sorry guy i am totally noob in this ~ i feel my vios damn slow.... 9.4sec after i done , light weight pully, mainford , fitler and all the normal modification that you can get from ACC shop... but i still feel that...