Ed: If I'd had to make a wild guess I would say because of tuning issues
I do have access to a car mechanics shop (in the family) and all the tools that come with it, including an exhaust gas analyzer (which I've heard can come in handy in this case). I'm personally not the worst mechanic myself, but a long way from the best. The leader of the shop on the other hand has about 35 years of experience in this field, so I guess it wont hurt to try.
I will make sure to take notes of how the tuning is currently, and also make sure not to damage the original airbox. I have already ordered the henry abe box, so if it doesn't work out, I will just put the stock airbox in and tune it back. But the looks I'm planning for with this bike is to eventually ditch the side panels and open up the space in between to make it more "streamlined" along with other modifications.
Do you have any pointers about where to start out with the jet sizes and such for this setup? Also I'm not 100% sure if the exhaust that sits on it now is the original one for this bike(?)