But a fuel filter wouldn't 'clear' itself in the moment it takes to turn off and restart the car, it's an instantaneous fix. Further, not every full-throttle pass results in this problem, it's very intermittant and the car pulls quite well regardless; it's AFTER the full throttle application the symptom might appear.

Sorry I wasn't clear about that in the first post, it will pass just fine but subsequent to the pass it may exhibit this laziness. The laziness is most obvious when starting from a complete stop, press the accelerator and it's very slow to respond, press further and it finally RPM build. It's not a slipping transmission, it's the engine not revving. It has recent plugs, O2 sensor, MAF and filter, there is no misfire or 'stumbling' like my old 440 with too much Holley carb on it way back when.

I haven't checked the codes though I have a scanner, I'll do that when kids get home from school (they used to ride in it, now they drive it!)...