Being OBD II, you don't change chips. You download software. Active has designed programs for people before, don't know the expense. Shark injector from Turner Motorsports or www.sharked.com
probably the best.
1995 325I, window tint, K&N, debaffled airbox, BMW #104 wheels, Nighthawk low beams, smoked side markers, smoked corners, smoked taillights, M3 stlye heated mirrors, various interior bits, Bosal cat-back.