997 642 159 01 is a DVD navigation drive applicable for a 997 Turbo in RHD spec vertical mount.
997 642 157 01 is a DVD navigation drive applicable for the 997 Turbo in LHD spec horizontal mount.
Of the two units the 157 is a better match , though its not the correct unit for your car. Since the DVD drive relies on both information from the satellite and pulses from the road wheels , it may be the turbo which uses different brakes has a different pulse signal , hence a different part number. Fitting this unit in your car may result in an error or offset in true location versus actual , that may lead to difficulties when driving in complex road networks or cities.
To get either DVD drive to work in your car, the PCM needs to be updated to level B software , which is version 3.0. Your PCM will require two software updates , the first to take it to level A the second to level B. After the update , the Navigation drive itself will probably require an update to allow use of the newer map DVD's. Don't forget that you will probably require a metal cradle, GPS reciever , cables and some fittings to install the missing parts in your car. These can only be sourced from Porsche , so can be expensive. One final word of caution, if your car has the Bose sound option , you need to be very careful about updating the software as the Bose amplifier may also require a software update, which if not done correctly can render the amplifier useless.
Though the update can be done by yourself , it's worth making sure you know exactly what to do before starting as an incorrect procedure can render the PCM itself scrap. The software disc to do the level A update can be bought in isolation from porsche , though the level B and DVD drive update software is sold as part of the map update pack which retails at about 350 pounds. Porsche will then charge an additional 1 hours labour to update the software on your system, though may be apprehensive if the navigation hardware isn't original factory fit.
