Gotta admit, since fitting the IA, mine dropped a bit too. Because I wasn't riding it properly.
If I do what I think is a 'commute ride'(sub 4k shift, light throttle) over national speed roads I get 42-45 mpg which is about 160ish to a tank.
I went out last week with a mate on a GSXR600 into Yorkshire on A and B roads where I was holding the revs longer, and doing an IAM style ride, I got 48mpg!!!!
Yeah I thought that was a bit odd too, but I've looked at my fuel consumption history, and its much the same. Been getting better tank range on faster ride outs than commuting!!!
I was getting concerned, as my carb'd R1 was getting high 40's and it only gets used on quick ride outs!!!