Under steering wheel the large panel is held by 3 plastic screws, which turn 90 degrees to loosen, and the panel can then be pulled out of its 'slider or sleeve' at the footwell end - short sharp tug.
Silver box with large black adapter/plug is visible at the front top right corner, just below the dashboard. 4x 10mm screws, 2 either side, are easy to remove, as 1 turn, and they're finger-tip loose. Bit fiddly, but OK.
The ECU will then come out, with firm tug in horizontal plane, straight out towards rear, and once out, the adapter/plug at front can be removed, by pulling open the silver clip, and sliding the adapter off the front of the ECU.
Take to table, keep clean ! On back are the 4 "torx screws" - make sure you have a screw-driver with this 'star' shaped head ! (I didn't). Remove them, bend back the lugs, and lift off the ECU from its silver metal cover.
My 1990 325i Sport had a yellow plastic case or protector over the top of the Chip, which needed to be gently prized-off, then the Chip is visible, and by lifting from its ends, lift one end then the other, and off she comes. Take new chip, and gently align the 28 pins into little holes, press gently once aligned.
Reverse above to refit. And yes, excusing short trip to borrow the torx screwdriver, 45 mins is realistic.
Started her up in garage....ran high on tickover (1800-2000) and then stabilised in steps, and after 10 mins, tickover is better than was before.
Off to take her for a 'full rev range run'
Tony
