Here is the virtual dyno comparison of a 3rd gear run before and after the exhaust install. The logs follow.
That's a pretty sizeable gain - 35 whp. Looking at the logs you'll see IAT differences of about 10-12 deg. That will negate some of the gains as cooler temps give more power but at close to the 100 deg mark I'm not sure it's that big of a deal. I'm not necessarily saying I gained 35 whp but the car feels quicker.
There is a big throttle closure with the new exhaust. This was literally on the drive home so there was no adaptation. I never felt it - as demonstrated by the dyno. My timing values are dead even.