before and after exhaust dynos

Has anyone here performed dynos directly before and after an exhaust and/or Power Commander install? It seems like a lot of us here have exhausts on our bikes now but there havent been many dyno comparisons to justify the $1200+/- spent. Dont get me wrong, the bike needs an exhaust for sound purposes alone but I want to make sure I'm getting the most performance out of my money as possible.

I'm particularly interested to see if anyone has a before and after dyno of the Akra full system. It would be interesting to see if its reallly worth the extra $700-1300 for the full system over the slip-ons.

I rode my first superduke for about 8 months before I fitted the cans and remapped.

My before and after test was trackdays at snetterton (UK track known for it's long backstraight)

Well worth the money!