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New plugs, wires filters during the resto. Fuel rail is spotless inside, injectors were all cleaned and tested, new fuel reg, all new vac lines, no leaks of any sort, everything works perfectly. At idle when fully warmed in gear, idles about 500-600, and fluctuates, feels like an occasional miss. Never stalls, and never hesitates off idle, runs perfectly otherwise. No stumbles or misses even at low rpm in high gear under load. Honestly, this car was off the road for so long I can't remember if it always did this. All I know is that my other "H" chassis car is silky smooth at idle. Thoughts? Mike.

I'd check the coil resistances, and if the ICM mounting points are clean for a good ground first.

Everything is spotless, and I already swapped the coils and the ICM. No change at all.

Mass air sensor? if you can figure out whether it is a random missfire affecting all cylinders intermittently or if it's a dead miss on a single cyl would help to narrow down the possibilities. good luck.

Kevin.