Nissan Repair: 94 Nissan pickup stumbling/hesitating, mass air flow sensor, air flow meter

Question
My 94 pickup (4 cyl 2WD - KA24E engine) is having
hesitation/stumbling problems only after it warms up --
about 10 minutes into the drive. It does it at idle,
acceleration, everywhere. I changed the spark plugs a couple
months ago. After the hesitation problems I've changed the
distributor cap and rotor, spark plug wires, fuel filter,
air filter, intake air temperature sensor and the oxygen
sensor.

I am getting a check engine light but the Nissan dealership
wasn't able to pin point the problem because the light only
comes on for a second and then shuts off. They gave me a
list of parts that it could be and I've changed them all
except for the air flow meter (mass air flow sensor) because
that part is more expensive and I don't know if that will
solve the problem either.

Any suggestions?

Answer
Jack,

Check out the following and read the codes for yourself.
 Find the computer control module and follow these instructions.  Then, email me back...
Nissan
11     Crankshaft Position Sensor
12     Air Flow Meter
13     Cylinder Head Temperature Sensor
21     Ignition Signal
22     Fuel Pump
23     Throttle Valve Switch
31     Load Signal
32     Start Signal
41     Fuel Temperature Sensor
44     System Okay
1.   Verify that diagnostic mode slesctor is turned fully counterclockwise.
2.   Turn ignition switch ON.
3.   Make sure inspection lamps stay on. (Bulb check.)
4.   Turn diagnostic mode selector fully clockwise.
5.   Make sure inspection lamps display code 23 and 31.
6.   Depress accelerator pedal and release.
7.   Make sure inspection lamps display code 31.
8.   Start engine, apply brakes and shift into "D" position.
9.   Make sure inspection lamps display code 31.
10.   Turn a load switch OFF-ON-OFF. (A/C switch, Headlight switch etc.)
11.   Shift into "P".
12.   Make sure inspection lamps display code 44. Any other code is a DTC.