How Much Vacuum??

Check your lifter preload!

Or get a second vacuum gauge; 6" is not right and would/should be giving you tuning fits. And 16* initial should be plenty. Mine runs fine down to 12* and even lower.
Yeah guys crank 'em up to 25 all the time, and if you have an automatic with a 2200plus stall, that works.
But it don't work so good in a stick-car;on account of a stick car typically idles at 6mph@750rpm, and there is no TC to absorb the power pulses, so they go straight into the rear springs.And then the car starts to do this little annoying bunny-hopping, and in a bit more time, the entire chassis gets involved.But by backing off the initial timing, the pulses are weaker, less violent. And once you get a good tune into it, you find out that just because she likes 25*, she can be happy with 14* or even less. Mine "likes" 7*@600; the bunny-hopping being all but gone. I suppose I could put some SS springs back there, but then the pulsing would go into the chassis and tires. Besides, I don't want those springs.
Yeah so,back to the top^