I didn't specify but if you do go for the 900rr header, would you be able to attach ANY slip on that fits WITHOUT doing a tune ?
I'm really liking those 3/4 Carbon Yoshimura slip-ons or if I could get my hand on one of those wrap around the swing arm pipes from Ferris Buell picture
Paging more technical ppl for input @LDH
Keep in mind how significantly mismatched a 900RR header is for a stock 919 engine.
Fueling changes are necessary in order to reasonably correct for that.
Without remapping, I'd predict the fueling in the low to medium revs and low to medium throttle positions to be lousy.
The primary issue is the 900 header, not the can one might use, a proper can assumed that is.
(unlike our European member from a few months back who made his own baffle as inserted into the header end, and absolutely strangled the engine).
A decent can just won't make it any worse.
If you want, download the free PC software for a PCIIIusb, and do map compare of the stock map to the few 900RR maps we have handy in the DropBox.
I think you'll see that as most insightful.
If you don't have access to the DropBox, PM me and I'll e mail them to you.