[jspaeth]

Is this why when I am cruising on the highway in 5th gear and then blip the throttle (just enough to build a psi or 2 of boost), it takes an extra 1/2 second or so for my AFRs to go slightly rich?

.....in other words is there really a noticeable dealy between the engine's operating conditions and when the air-fuel gauge detects the mixture?

If so, this screams for the need to do steady-state tuning in those portions of the map