If is the display for the wideband o2. The car no longer has a MAFS, and the fuel computer, (AEM in this case) pulls the wideband reading to calculate fuel.
He is leaking boost at 26psi because the wastegate spring is too soft, once that is fixed he will run 30psi to redline. He is also having issues with boost spikes because of the AEM. Once it is all fixed, he will spool fast (about 1000rpm faster) and hit 800+
that is one of the better sounding dynos i have seen/heard. also, ive never been at a dyno but i thought that the speedometer doesnt move when you are doing a pull? i thought speed was measured by the non drive wheels?