In an effort to summarize what has been learned so far, Ill start with the Carrera instrument cluster itself. The assumption of the DIY is that the instrument cluster is fully functional. I have a concern with the instrument clusters found on the internet auction sites. Did the seller just decide one day that he didnt need the instrument cluster in his car? Or, is it available because it was removed from his car for cause? I would put more trust an established re-cyclers parts because the instrument cluster in the donor car was probably working properly before the accident and, given no physical damage to the instrument cluster, probably still does. I also have doubts about the viability of an instrument cluster that has had the part number and/or serial number removed.
Anyway, the basic MY02 MY04 Carrera instrument cluster is the same regardless of the car it is installed in. There are different part numbers for manual vs. Tiptronic and color coordination of the instrument faces to interior colors, but the instrument cluster is functionally the same whether it is installed in a C2, C4, Coupe, Targa, etc. Only the coding by a PST2 / PIWIS tailors the instrument cluster to the car. (Instrument clusters from Turbos are a different breed and should NOT be considered for a transplant.)
The ideal candidate for a transplant into an MY01 MY04 Boxster is a Carrera instrument cluster taken from an MY02 MY04 996 C2 Cabriolet. (Obviously, consideration has to be made for the type of transmission manual or Tiptronic.) This means that the instrument cluster is coded for the proper fuel tank/fuel quantity transmitter and the Convertible Top Warning Light. If the instrument cluster is taken from a Coupe (or Targa), the Convertible Top Warning Light will not illuminate when the Boxsters top cover isnt fully stowed. Some people can live with that anomaly. Likewise, if the instrument cluster is taken from an MY02 - My04 996 C4 Coupe (or Targa), the fuel quantity will be inaccurate. In order to make the instrument cluster operate completely, if not from a Cabriolet (or is from a C4) your car's DME will have to be temporarily re-coded. This is because the Carrera instrument cluster has to see a Carrera DME before it will allow its coding to be modified. (More on DMEs below.)
MY97 MY00 BOXSTERS. For RennTech members who have MY97-MY00 cars and who are contemplating installing a Carrera instrument cluster, the following might be of some assistance.
You must find a Carrera C2 instrument cluster. The C4 / C4S instrument clusters are physically (internally) different and there is no hope of getting the fuel gauge system to indicate fuel quantity accurately. I would also recommend looking for an instrument cluster from only MY00-MY01 Carreras. This is because the MY98 - MY99 Carreras use a different fuel quantity transmitter than your Boxster so a MY98 MY99 instrument cluster may not be compatible with your Boxsters fuel quantity transmitter. Also, a MY98 MY99 instrument cluster may not have provisions for the On Board Computer. Your ideal Carrera instrument cluster would be from a MY00 - MY01 C2 Cabriolet.
From the 2005 PET parts list, the following part numbers are representative of the MY00 MY01 Carrera instrument clusters that would be good candidates. These instrument clusters are matched to your Boxsters fuel quantity transmitter and have electronic mail which I would guess is Porsche parts manual speak for On Board Computer message display capability.
MY00 MY01 Carrera C2 6-Speed 996.641.105.02.70C
MY00 MY01 Carerra C2 Tiptronic 996.641.106.02.70C
MY00 MY01 Carrera C2 (GB) 6-Speed 996.641.107.02.70C
MY00 My01 Carrera C2 (GB) Tiptronic 996.641.108.02.70C
For reference, the MY98 MY99 Carrera C2 instrument cluster part numbers are the same as above except they are 996.641.###.01.70C.
DME CODING. A procedure has been used to successfully code a 986 DME as a 996, code the instrument cluster to C2 Cabriolet and finally recode the DME back to 986. I would strongly suggest that the person following this procedure be an experienced PST2 / PIWIS operator. There are several steps (key strokes) needed to accomplish the coding.