[Gelbster]

The oil issue for the 6 speed has been discussed at length - notably with info from Smallblock454.The general conclusion for both 5 & 6 speed is that anything other than the correct spec is an ill-informed and expensive choice.Following is for 6 six speed only.
http://986forum.com/forums/boxster-general-discussions/55977-2nd-gear-hard-shift-after-tranny-oil-change.html
http://986forum.com/forums/boxster-general-discussions/62319-2nd-gear-issues.html
http://986forum.com/forums/performance-technical-chat/59344-gearbox-8620-1003-boxtser-s-04-2003-a.html