If you have all the mods, it is good to get a chip to help dial in the changes your car will have. But for a 98 M3, the computer system is OBDII. For that, you'll have to do some sort of flash programming. It costs around $399. I have also heard that Dinan is only effective on wide open throttle. From reading posts on this board, they say that the Jim Confronti programming is the best. I have an intake and exhaust on my 98 328. But I don't have a programming upgrade because I've heard so many "iffy" things about it. Some say that they love the difference, while others say that they can't feel any difference at all. I'd rather spend my money on a set of sway bars.