what year is your car? I would say if you have an OBD2 i.e. 96-2000, get the book for the 99-00 si. If you have an OBD1 car (92-95), then get the del sol book. If you have and OBD0 (88-91) car like I do I just got the del sol book. The one I got has all the del sol motors so it has specs for my d15 which i still have in my car, and it has the specs for the b16 i am building. The differences in the books are really only going to deal with wiring and OBDs and that is pretty much it.