First step is to disconnect the battery to reset fuel trims.

Next, go over to the passenger's side footwell and remove the piece of plastic trim on the right hand side in front of the door. It just pulls out. The ECU is held in with two T25 or Philips screws depending on car. Disconnect the ECU. On the underside of it there are some metal tabs you have to bend away to take the lid of the ECU off.

Once you take the lid off, with the connector pointing up the chip goes in the bottom right corner of the ECU. It's under a little plastic retaining clip. Make sure the notch in the chip matches the notch in the socket or the car will not start.

Now put it all back together.

The EZK is in the front of the passenger’s side footwell, under the big piece of felt under the glovebox area. A few quarter turn fasteners hold the felt in. You should see a little black box with a smaller version of the connector that the ECU has. To my knowledge no 240s were sold with gold EZKs.

The EZK is held in with a big spring clip. Push down on one side with your palm and reach around the EZK to unclip the spring with your fingertips. It's easier to free the spring clip on the connector before you remove the EZK.

Once you get it out, you should see four T10 screws holding the rear half of the case on.

In there you should see the big main board and a second board perpendicular to that one with a chip identical to the fuel chip on it. Some EZKs do not have this. If you don't have the daughterboard you can buy a "chippable EZK" which just plugs in in place of the one you have or a daughterboard kit if you're into soldering.

After reinstallation, you're done.