Just ordered the Akrapovic carbon fiber full race exhaust without the cat. The Akrapovic cf exhaust is 10 lbs lighter than stock.
The specs on the BMW website say that the emissions system is closed loop (needs to be with a 3 way cat), so it should be constantly fine tuning the fuelling to stay at the right air fuel ratio to keep the cat working at maximum efficiency. If systems haven't changed since I last delved in to this kind of thing, the ECU will have a base map for the fuelling covering the speed and load range, and with feedback from the O2 sensor it will fine the map if it stays operating at any one condition for long enough. What you don't know is whether BMW has bounds set on the amount of tuning within that map that is possible - eg the new exhaust could change the fuelling to get to stoichiometric by more than amount of fine tuning the closed loop system can achieve (but as the new exhaust does not have a 3 way cat, that isn't really so much of a bother).from what I understand you do not have to tune or use a fuel management system.
That bit where it saysThis was on the website.
suggests that the closed loop control on the bike still has ability to tune the mixture - but while stoichiometric keeps the cat working at max efficiency, it means it doesn't allow lean off for economy or going richer for WOT power... hence their recommendation to get the most out of their exhaust."No fuel remapping required, but for optimal performance RevZilla recommends use of a fuel controller"
It's possibly a standard statement they use for all their systems - which would make sense. For a 3 way cat, to pass emissions regs, the fuel air ratio must be tightly controlled - but if there are no requirements or rules to pass the need to keep a cat working at its maximum efficiency is no longer vital, it will still reduce emissions with non-ideal fuel air ratios but just not as much as it is capable of.It said the same for the Stainless Steel model with the cat also.