BEWARE, the Rabbit Hole!!
I have posted in several other places and posts about my forray into this venture.
Simply stated, the two CHEAPEST / effective methods for adding dual exhaust are:
1. Find a used Muzzy's Dual System. Full stop.
2. Find a used ZX14 dual system including header.
Remember that the hardest parts of this conversion will be finding / sourcing / fabricating a left side exhaust hanger, and modifying the center stand. There are ALOT of hidden costs to this swap, be warned!
Also, you'll need to upgrade your ECU / Tune to accommodate for the new pipes.
Steve offers an AreaP Flash that is not specifically designed for duals, but works, depending on the type of header you utilize on your system.
It is WELL established that a slip-on aftermarket muffler with the OEM 4-2-1 header on the C-14 with Steve's Flash, will produce more USABLE low-end and mid-range power than any dual aftermarket systems. FULL STOP.
Properly set-up and tuned Duals, are better at making more power Higher in the rev-range.
If you want a DUAL exhaust LOOK, then sourcing a used ZX-14 header and cans, or with aftermarket slip-ons will be your cheapest, most available option.
good luck.
gr
PM me if you have questions.