164 Erratic running - Fairly long

["Daegrigg (Don)" <daegrigg@domain.elided>]

I am pulling my hair out on this one so I ask collective Digest input.

91 164S -  Starts fine cold and warm but after a few minutes and/or loading the engine the check engine light lights, idles goes down to about 1000 rough.

Idles high on start up about 1800 2000, stays at about 1500

Can clear the check engine light by pushing accelerator to the floor; car returns to idles, light goes out and returns after idling.  Error code is 1223.

On the road, car runs well for a few miles then looses power. 

What I've done:

1.  Checked resistance reading on the AFM and it per spec.
2.  Took off AFM works cover and cleaned the inside with contact cleaner. 
3.  Changed rotor,  Cap tooks OK> 
4.  Check high voltage coil wires, clean and dielectric greased.
5.  Clean connections to the AFM. 
6.  Clean connection to the RPM sensor
7.  Checked hoses, again and again.
8.  Idle actuator seems OK - idles is smooth if a little high until the engine goes off song.  See above. 
9.  Replaced the infamous one-inch section in fuel pump last fall.  Car starts fine from cold, overnigt iindicating system in holding pressure. 
10 Fuel pressure regulator changed in November. 
11.  Checked connections to O2 sensor that was replaced last summer.

Son drove car home from school, 300 mile trip, car was idling very rough, power was low and every 3 miles approx. the car would lose power and stall over the course of a min or so. When this happened giving throttle had no effect on rpm however when put in neutral giving throttle resulted in rpm going up but with trouble.

I am suspect of the AFM but unsure how a bad one would behave.  Could the one-inch fuel line be leaking even though car starts OK?

Observations, experience, help  appreciated.

Thanks, 

Don
Fred.  Any conclusions?
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