Got any more ideas? Please?

[Roa, Greg]

Still having a idle/low rpm missing issue with my 87' 5kcstq.  The car runs very well when started, and until it has warmed up for a minute or two.  When warm however, it idles with an occasional misfire.

It will run good for a few seconds, then I'll get a stumble, then good for a second or two, and another stumble.  Then it will run good for a second, and stumble twice quickly.  After this quick stumble, it will run good for a few seconds, then the cycle starts again (always the same pattern).

So far, I've replaced:
Several old vacuum lines
idle/wot switch
all 5 injectors/seals (with new)
O2 sensor (new bosch)
Fuel dist (used spare)
plugs (correct bosch)
plug wires (new bosch)
cap/rotor (new)
-also has a new pierburg fuel pump installed by PO (about 3k miles ago)

Also I've:
cleaned/lubed ISV
verfified coil resistances
dumped codes (always 4444, even when I stall the car)
checked for stumble/stall when pulling dipstick and oil fill cap
checked temp sensor resistance values
swapped out ECU's

At this point there's not a whole lot else that I can think of to check.  Car runs great except for this.
The only thing that I have left as a suspect is the dist hall sensor.  The connector is not very secure on the dist housing, and I don't know if the wires to it are in the best shape.  I don't think that would affect the car in the way I am seeing though.

When I check the duty cycle, it fluctuates more than I would expect, as does the o2 sensor voltage (I suppose because of the misfire).  The duty cycle tends to swing around 36%.

I'm confused.  Someone help me out with some ideas!  I'm longing for the simplicity of my 4kq's.

Thanks!
Greg Roa
Cincinnati, OH
86' 4kcsq x2
87' 5kcstq
93' 90CS
83' 944