Oh dear, what a difficult question...
If it was mine, I would junk the headers (too small) and buy either a set of US headers or pre-08 UK headers (these are the same as the US headers but need a lambda boss welding on). I think there are some in the for sale section.
Then I would fit an Albert666 (see
THIS post - you will have to trawl through the 1125 pictures and chat), a Remus (not everyone's favourite), a Free Spirits or a Stealth (never had one but they seem to be popular)... All these need to be to fit a pre-08 bike to fit the headers... And all the above are stainless, which is a must as a painted exhausts don't last long before they go rusty...
Alternatively, PM tubbs and ask him to rework a standard exhaust for you. Again, I would go for a pre-08 muffler to go with the headers.
As for fuelling, depends who you ask. If you ask me, I would say:
Quote:
Provided the exhaust header lengths do not change, the closed loop control of the Buell ECM does a good job to accommodate change in air filter or exhaust. Remapping will make it better, but it wont run badly with the original map.