The problem is that BMW decided to stop the Chipping with the '95 build year.
They added a security feature to the chip itself that is different for each car.
If your ECU number ends in -404 you can just plug in a chip.
If the ECU number is -484 then it has to be flashed with the BMW service computer or sent to the chip provider for programming.
I use Wokke_2000 chips from Germany. Put them in an E32 740 first and when I test drove the 840 I couldn't understand why it was so much slower. Then I chipped the 840