Fazer 600 sounding like exhaust blowing but it isn't

[floism]

All the studs were changed when new downpipes fitted.
No air coming from around any of the joints and normal noise from end can (Standard can).
Sound like the noise is coming from the engine rather than the exhaust.
Just spoke to a friend of mine (Wish i'd spoke to him before posting lol) and he said because i put E10 in it and then left it stood it could be water in the fuel system that causing noise when engine warms up.It's a stab in the dark but i'm going to drain fuel system this weekend and get some superplus and give it a go.
Thanks for your reply BBROWN1664