How can you increase the acceleration on a 2001 325ci?
lighten car and or add more power,
do what ever you feel is to get your vehicle light as possible.
add more power. your engine is already pretty efficient so adding power will be about how much money you want to spend, i would highly recommend to use dinan parts, find a BMW dealer ship that is dinan certified and you can have blowers, cams, thorttle bodies, software, there are many different things you can do to add more power, it all depends on how much money you want to spend for speed.