if you are looking to grab temp and pressure info, here is what i know. neither is available via obd.
temp info is available via the oil level sensor in the sump, however the signal is proprietary and has to be converted - here is how to do it ...
https://rennlist.com/forums/996-forum/827720-oil-temp-gauge-using-the-built-in-oil-temp-sensor.html
durametric is able to grab temp data at the diagnostic port so should be easy to get, or you can mount a vdo sender in the head in a spare port under the airbox and run a wire.
for pressure, as steve says, the boxster has a vdo pressure 'switch' to trigger the idiot light. if you want analog pressure info, you have to replace the switch with a sender (located in the head in a port front right); you can use a vdo sender or the oem porsche unit used on the 996 (same diff). another solution is this ...
Smarter Idiot light
regardless, i think it requires running new wiring, as porsche 996 schems show pressure sender wiring as a discrete wire and 996/boxster engine harnesses are fundamentally different so do not anticipate the spare wire being available. will also have to interface w your unit in some manner; jk notes the plx interfaces, or perhaps consider something proprietary for just your unit - presume you will build a harness to plug your unit into the diagnostic port; leave a spare connector for those that want to install a vdo pressure sender and run the wire forward.