When looking at the activity of the "crossover" I believe that the basic
fuel injection is out of adjustment and will cause an overactive
crossover.  In other words if the fuel injection system is in proper
adjustment, you should be able to disconnect the O2 sensor, and read the
voltage from the O2 sensor black wire.  Open loop voltage is very stable
and should be in the .5 volt range.  Anything consistenly above .8 or
below .3 volts needs to be corrected.

When the system is really tuned the O2 sensor will not crossover as
rapidly as a system that is too rich, .8 volt or higher, weak vane
spring setting, malfunctioning fuel pressure regulator too high system
pressure, Or too lean .3 volts malfunction of fuel pressure to low or a
poorly adjusted afm wiper.  Other variables could be the cause of either
problems, but this is where I would begin.

Sincerely,

Mark Keller
91 Carat