The final drive is between the trans and the engine and if the TIP is over filled you will build up to much pressure and force TIP fluid into the final drive. If the final drive gets to much fluid there is a air hole above the final drive axle cover. If the oil is leaking where the two connect, it's most likely the RMS. TIP fluid has a very distinct smell over engine oil. I have a leak on my drive side of the final drive unit and will need to replace the seal...maybe you have the same since this is a common area for a leak.
Go here and view or download parts catalog and you can see the TIP diagram:
http://www.********************************************.com/porsche-parts/boxster.php