hello Fastraxsg
The side pipes on my cobra (and the headers) are home made.
the construction is revealed in this picture
As you can see the headers go into a collector (part of the header kit I brought) and then from the collector into a 3in pipe with a 45deg bend and straight into a 90deg bend to get the pipes to the side of the car.
After that it just steps up into a 4in pipe.
These now have tips made from sawn-off 4in mandrel bends and home made inserts to add muffling.
got the bends and joins etc from local exhaust centres. Having a home mig and a brother who can use it made the construction a lot easier - everything bespoke.
Others here have done the 4-pipes thing - maybe next time for me
hope this helps
LoBelly