Hi there, looking for advice on what larger bonnet scoop fits directly onto a 2006 xten forester and also looking for a good sounding back box.. any advice greatly appreciated. cheers

I believe the STI scoop from the bugeye Impreza STI is the same fit, and stands about 3/4 of an inch higher.

 I have the same model as you, and for the back box I have a Hayward & Scott 'Straight Exit Jap Style 2.5" Backbox with 4.5" tailpipe'. It sounds awesome!

I agree about the h&s systems. 

H&S afterburner vortex back box is what I have, sounds good (I think anyway. My neighbours might not think so though!)   

Not sure about the scoop situation though.

if you can't find one then you could make 1 up.

Mine did not fit, because at the time there wasn't one for an sf5, so I made it fit. I cut the bottom off & re-fibre glass'd the bottom area shape, so I could fit it to my bonnet. Reusing the oem slider bolt things. So it bolts straight on like oem.