Scorpion cans offer a slight perf increase and is what my local bike shop recommended for Yamaha's, there is one on ebay. I would call the guy and haggle on price as he is on a trip with that price and the postage is 3x what it needs to be.
http://www.ebay.co.uk/itm/YAMAHA-FZS1000...3f3abacda2
I had a BF on my FZS and didnt like the sound so when an acro came up cheap I grabbed it. Found an Acro going cheap on ebay, the R1 link pipe looks similar to an fzs one, but you may need to get an fzs link pipe for it though.
http://www.ebay.co.uk/itm/akrapovic-tita...4d226ce81a
http://www.ebay.co.uk/itm/YAMAHA-FZS1000...3f3abacda2
I had a BF on my FZS and didnt like the sound so when an acro came up cheap I grabbed it. Found an Acro going cheap on ebay, the R1 link pipe looks similar to an fzs one, but you may need to get an fzs link pipe for it though.
http://www.ebay.co.uk/itm/akrapovic-tita...4d226ce81a