Have you read the 'Similar Thread links' below yet? once you start reading one or two and their 'Similar Thread links' you can get reasonably informed fairly quickly and saves searching.
Most of the shorty exhausts are just slip on mufflers in which add noise more that power/torque. Now if you want to add more power/torque (with added noise in most cases) than a slip on will provide look into adding header instead of using the manifold. The header will let the engine get rid of the exhaust much quicker....breathe. Another words compare prices with just adding a slip on to adding a header plus maybe a louder muffler. You might be surprised on how close the prices are to just adding a shorty to adding a full healthy exhaust. Some members have added shorties but when all is said and done they have went with full exhaust. Spending money that could have been used on full exhaust.
Check out Viking exhaust. He can set you up with a shorty or full exhaust. Contact member Paul Bryant and talk to him. Has a pretty good payment plan as well.
No inconvenience, just starts the conversation a little informed to understand feedback like Mully95's and Steel's as to the why etc. I did spot a cheap modified header going on US eBay tonight. No idea of manufacturer and not equal length pipes like Aussie CES or Reband or NZ Viking but appear to be an improvement on stock manifold. Someone here is likely to know of them or you may find info in a search of the forum but I had no luck googling them. 04-09 TRIUMPH ROCKET III EXHAUST HEADERS PIPES JS
Price:
US $125.00 + $74.94 International Priority Shipping to Australia
best power and sound I rate "CES" for my money followed closely by "Rebands" and "Vikings" for best finnish and if you are planning to go up into Hi comp (hi comp pistons) Hi rev (big Cams) areas then the Carpenters but the first three will give you the best usable power for on the road even if you go with the Lushy Street cams and hi comp pistons