Slant 6 power issues

If I adjust the timing at all in either direction it gets worse, so I know it’s not that. I’ve messed with the idle screw. It runs fine at idle, but why doesn’t it make any power anymore?
I believe you may have multiple problems; related to retarded idle-timing. But it could just as easily have been overly-advanced before. So then, you gotta start with properly setting the timings.