That's the VarioCam actuator solenoid valve on the passenger side (Bank 1 like paulv said).
I just had mine replaced last month for approx. $1300. The engine does not have to be dropped. The coil-packs and plug tubes are removed, 2 bolts on the VarioCam cover removed, 4 bolts on the oil-pump removed, 23 bolts on the cylinder cover removed and then 2 bolts attach the solenoid to the actuator.
The solenoid itself is about $180. The pin/plunger on mine would move only a fraction of an inch when 12 volts was applied- I checked after it was removed.
Download this file...
http://www.cannell.co.uk/Boxster_Manuals/986%20Group%200a%20Diagnosis%20To%2045.pdf
Go to page 24 45-D for the diagnostic procedure.
I was getting 12v at the connector so the wiring was good up to the solenoid.
PM me if you have any other questions.
Regards,
mike