Dont believe the hype that the 01-05 brake booster is a better design. This is all bs from lexus. My buddy rebuilds these units and compared the two and the internals. They are pretty much the same other then the pressure sensor. Dont how much you picked up the 03 booster for, but keep in mind that the motor pump is the same as the 98-00. Its just newer and people think toyota redesigned it, but not really. Anyways, sorry for commenting on this.
Let me know if you need any advice on it.