If you can't find a sweet spot through the whole swing of advancing the IP, maybe its time to change your timing chain. Sounds like you've twisted all the timing you can get out of the slack in your worn chain.

Twisting the top of IP toward the engine advances timing, usually getting more power until you go so much as to create knocking, then power drops off again.

You think the problem of no power is timing advance related, but it's probably just timing related - your valves are not in sync with the piston position. No amount fuel delivery timing compensation will correct that, only a new chain will get the opening and closings of the valves sync'd up to the compression stroke. When you do this, the smoke at idle goes away. Trust me, I've gone through this whole cycle.

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Cheers!
Scott McPhee

1987 300D