I think that a quick look at this site, shows that there are but a few porsche's that can top a 13 second quarter mile.
http://www.ssmoparmuscle.com/speedcomp.htm?NORDERBY=make&OORDERBY=make&OORDERDIR=DESC
The point I was trying to make about the other page is that most of those car's are enthusiast/modified cars not off the shelf, standard porsches.
For example:
Porsche 911 Turbo Roock RST 650 2003 (insane, not std)
Porsche Carrera GT 2004 (supercar)
Porsche 911 Carrera Turbo 1988 (old, and likely modfied as stds were much slower)
Porsche Ruf R Turbo 2002 (insane, not std)
Porsche 911 Turbo 2001 (std time is around 12.3 for these, likely modified)
Porsche 911 Turbo EVO Stage 4 2001 (insane, not std)
Porsche 911 Turbo Turbo S 1997 (possibly std - my mate has one of these)
Porsche 911 Turbo X50 2003 (upgraded)
Porsche GT2 (supercar)