Installing the RaceChip took around 1h20 including taking the photos as I went.
The part that took the most time was releasing the clip from the common rail pressure sensor. This was due to the rotation of the sensor on its screw mounting that shielded the release lever for the clip. You must lift the release clip slightly before pulling the plug off and this proved most challenging. Other engines may not have this problem and hopefully the clip will be exposed, reducing the time to fit the RaceChip.
To install the RaceChip on a Citroen C3 16v HDi, follow this guide.

- Remove battery covers, air intake plastic and disconnect the battery
Remove the battery cover and disconnect the quick release battery connector.

- Remove the air intake pipe
Remove the air intake pipe from the engine bay. There are clips holding it to the engine.

- Unclip the purge bulb
Lift off the flat engine cover and unclip the purge pump bulb from the air filter box

- Disconnect the turbo pipe, MAF connector and air filter lid
Disconnect the MAF plug from the MAF, the turbo pipe from the turbo by slackening the jubilee clip and unscrew the 3 cross head screws on the air filter lid. You can then remove the pipe, MAF and air filter lid as one. There is no need to break it down.
Lift out the air filter.

- Remove the grey H section from inside air filter box
Removing the H section from the air filter box will allow the air filter box to separate in to two parts making it possible to remove them from the engine bay.

- Unclip the fuel filter
Unclip the fuel filter but do not disconnect anything from it. There is enough free pipe to allow it to move out of the way without having to disconnect any fuel or electrical connectors.

- AIr filter box removed gives access to EGR valve
With the air filter box removed it is now possible to access the EGR valve. The EGR valve is directly above the common rail pressure sensor.
If you have the original factory EGR clip on the silver colour pipe then the only way to remove it is to destroy it. The Citroen factory fit EGR clip is not re-usable. A
replacement EGR clip (here) is cheap and is designed to be re-usable. The re-usable EGR clip is released by undoing the hex head threaded bolt.

- Unbolt the EGR valve
With the EGR clip removed/slackened there are two bolts that mount the EGR to the engine. The pneumatic connection can stay connected but it is easily disconnected. Check for split rubber on the EGR vacuum pipe.

- EGR removed reveals Common Rail pressure sender
Wit the EGR valve removed it is possible to see the Common Rail end with its pressure sensor. Remove the plug from the pressure sensor by lifting the tag of the plug and pulling the plug body (not the wires).
If you want to see how to disconnect the plug from its socket, pick up the racechip loom and there is a pair of plugs and sockets to practice unclipping with.
The clip of the actual common rail pressure transducer plug on this car was rotated away from view, so releasing the clip had to be done by feel and a small allen key to reach between the plug and the engine. The angle of the allen key meant I could reach between the sensor and the engine because there is not enough room for fingers and I couldn't get a flat bladed screwdriver in there either.
This job of releasing the fac took the most time.
Be careful not to pull the wires of the plug.
A flat bladed screwdriver can help open up the gap between plug and socket while the clip is released. The plug was very tight and took a lot of wiggling around, even after it was not longer being held by the clip.

- Connect the racechip socket to the plug you disconnected
Connect the plug you have just disconnected to the racechip suplied loom.

- Connect racechip plug to the sensor
Connect the racechip plug to the common rail sensor.

- Fit the racechip control box to the car
Connect the large plug to the racechip control box and find a place to attach it. I chose the battery compartment, next to the engine ECU. Two double sided sticky pads keep it fixed, yet easily removable should the battery need to come out.