Multiple random misfire PO300 97 GMC Sonoma

V6 Vortec with 80000 miles.
About 3 months ago, sitting at a light, the Service Engine Soon light came on and the misfires started.
Have replaced, in this order:
* fuel filter, one bottle injector cleaner in the tank, spark plug wires, * rotor and cap, air filter, mass airflow sensor (it threw a PO102 once), * Crank sensor.
After replacing the asterixed parts, the symptoms disappeared and the light turned off--only to come back in a day or two.
Compression and timing check good.
Tends to misfire more when cold, and when decelerating.
Runs better with MAF unplugged, before and after replacing it.
Misfire is visible using a spark testing tool.
Haven't replaced the coil pack or high voltage ignition module, but I see from threads here that this could be done--I just don't want to throw more money at it.
Any educated advice is welcome!
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This will be my contribution:
http://users.eastlink.ca/~smackie/p102.pdf http://users.eastlink.ca/~smackie/p300.pdf
Steve

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Analyzing the enhanced OBDII data might help..

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