Thats it ^ G052 911 is the stuff for the 6-speed manual and G052 145 is for the diffs in the Tiptronics. Called 'Syntrans Transaxle 75W-90', although oddly I can't find it on Castrol's site. They may have renamed it?
I first got Syntrans from TPS in favour of the OEM stuff which, frankly, is rubbish. I had an 01E 6-speed which had become nearly unusable on the OEM oil, even after a couple 30K changes. A change to Syntrans and it lasted another 60K so consequently I put it in everything
Comma make an equivalent fully synthetic 75/90 too which can be easier to get on the high street than the Castrol.