OK now we are getting somewhere.
Here is what I think you have done; With 14* initial plus 15 to 20 in the can, it is now idling on around 31* timing. This is reflected in the 19 inches of idle vacuum.So to get it to idle at 650 to 700,you had to back out the curb-idle screw, waaay out.By doing that, you shut off the transfer ports and had to give it idle fuel from the mixture screws,which now are richened up. So now it seems to idle pretty good, right. Right up until the engine sees a load, or you gently step on the gas. EDIT: and here's what I think may be happening;The load drags the rpm down, which causes the timing to EDIT; start to drop out, which immediately causes the engine to want more fuel, but since the transfers are dry, she can't get any gas, so she goes lean and dies.
Sound about right?
"Where's your T-port sync set at?"
Here's what you need to do;
1) Defeat the Vcan
2) Get your T-port synced up, and
3) reset the timing to 14* at 700rpm
4) verify the float level
5) reset the mixture screws
6) put the Vcan back on the timed port
7) Prove the power timing is limited to 34/35;whatever it takes to stay out of detonation. And more is not necessarily better.
the T-port sync is right when the exposed part of the slot, under the primary blades ,is looking like a little square to a little taller than wide.Once this is established try not to dink around with the curb idle screw any more than about 1/2 turn,either way .
If the idle speed does not dial in with the T-port synced, then you have to use the secondary cracking screw to fine tune it.
If you have a carb with no idle fuel on the secondary side, sometimes the engine doesn't like very much secondary air.If that happens to you, you will need to figure out an alternate way to give the engine the air that she wants, but do not stray far from the T-port sync..