Hi Mark,
I have some experience of this as my local Porsche Centre supplied me with the wrong "Sports Tails Pipe" (This is the name used in the original Tequipment brochure for the 993, big oval pipes). There are different sports tail pipes for standard body and wide body cars and different again for the Turbo. The standard body pipes are straight through, i.e. the inlet and outlet pipes are in line. The S and 4S inlet and outlet pipes are offset. The pipes for the standard body are interchangeable between left and right, the wide bodies are not. Part numbers as follows :-
Carrera and Carrera 4: 000 044 200 01
Carrera S and Carrera 4S, left: 993 111 981 02
Carrera S and Carrera 4S, right: 993 111 982 02
Turbo, left: 993 111 981 01
Turbo, right: 993 111 982 01
They look great but are bloody expensive.
As you can see I am really busy on a Monday morning. Aren't recessions great !!
Cheers,
Mark Thompson