Re: 900RR-W Aftermarket End Can
In theory your bike will run a little lean if you put a new can on it that flows better than stock. However, a new can in itself is not likely going to affect performance or A/F ratio enough to be any harm. I would recommend the jet kit to actually gain performance to go with the new sound, but it isn't "required".
/**Serenity**\ 2002 Honda CBR954RR Fireblade
"But risks must be taken, because the greatest risk in life is to risk nothing. Only the person who risks is truly free."