340 -727 -3000 stall- Vibration under load - Trying to find source

CudaFactHackJob said

If it begins to decrease when rpm is increased, it is NOT balance related.

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What makes you say that? If your RPM increases your vibration becomes faster to the point where it doesn't feel like it did at lower RPM.

Well changing the converter didn't cure it but we now know it is in or on the engine.