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Re: running rich under boost

     The mixture control system goes open loop at WFO and mixture is
     controlled by the map in the EPROM based on inputs from various sensors
     but not the O2 sensor. An LED mixture display will no longer "bounce" and
     should display a "richer than normal" mixture at WFO, though not a full
     1VDC from my experience. I always wondered if open-loop mode was
     triggered by the WFO switch or by the boost level, guess it must be boost
     level triggered if you are seeing open-loop operation with the WFO switch

Explicitly as it applies to the UrQ line -- the early "B"-suffix ECU
runs "open-loop" only at WOT (or cold, etc.); the later "F"-suffix ECU
does indeed go open-loop around 4PSI, as best as I can tell/recall.