This is also caused by the fuel lines in the tank. One will get out of position and foul the "anti fuel surge" flapper at the bottom of the fuel feed neck.
There is a TSB but I couldn't find it.
It consists of:
1 Pull the fuel pump (access under the battery on C2)
2. tie wrap the fuel line out of the way against the pump assy.
3. reassemble
Found it
TSB 911 (996) 5/99 2015 Fuel Tank Hose Modification August 12, 1999
If you are a
member of Renntech,
http://www.renntech.org/forums/tsbs/carrera/, it is listed in Under DIY tools in Porsche TSBs