So, I just spent some time on the phone with Vince.
To sum it up, the boost is nothing to worry about. The car (as you can see by the HP curve) continued to make more power with the higher boost (+50whp over spring pressure run), even though it looks like it is tapering off.
There are many variable at play (including VVEL, and the dyno MAP sensor), and since the car already made very good power, there was no need to spend a lot of time with the EBC setting to try and flatten out the boost curve. It also takes extra time to really dial in an extra few psi (small increments over base pressure) of boost with the EBC like we are trying to do here.
Vince felt like the kit performed very well and made power with ease.
Here is a better looking dyno graph as well:
