Something in the enrichment circuit. On my '85 the warm-up regulator changes the control pressure when there is a drop in engine vacuum (ie. stepping on the gas). Not sure if your '92 is similar, just throwing it out there.

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1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma

These things are such nightmares. I have a 93. How's your gas mileage? Wiring harness replaced? May not make any sense, but it seems to me the wiring harness is pretty much the non-obvious suspect for mystery diagnoses; if it's orig, what you are doing is surgery on a person with no brain

There is always the possibility the ignition control unit or even a coil could be weak and unable to make enough heat to light the fire under load. As I'm sure you know the KV requirement doubles or triples during hard accel. Just a thought
Bill