There are a couple of types of bulbs used, for gauge illumination and for idiot lights. From the Porsche spec book:
2W BA7s
1.2W W2x4.6d
Translating further, from PET, Porsche part numbers:
N 017 751 2
N 017 751 2
And, superceding to items carried by Pelican:
900.631.103.90 4W #3893
900.631.132.90 1.2W #2721
And, a link to the light bulb page on Pelican, for those who need it:
http://www.pelicanparts.com/catalog/shopcart/911M/POR_911M_ELlite_pg8.htm#item35
Hope this helps,
JR