DOES ANYONE KNOW IF REPLACING THE CANS ON A 2004 R1 (UNDER SEAT VERSION) WITH AKRAPOVICS SHOULD I REPLACE THE 'Y' PIECE OR KEEP THE ORIGINAL ONE?

THANKS IN ADVANCE

You can do either, but you may want to remove the cat from the Y piece to get the best from your Akro cans. Or do the same as me & de-baffle the standard cans & de cat the standard Y piece (end up with basically a straight through system ). For a fraction of the cost.

But as you have brought the Akro cans why not get the Y piece to go with them ???

I always do some replacements when I work on the bike before the pieces are done.