Idle drop by 500 rpm?

With your secondaries cracked open you are loosing all of your vacuum at an idle, then in turn your vacuum advance is doing nothing because there is no vacuum there to pull the vacuum advance so it dies when the idle drops when you put it into gear.

Over the internet diagnostics, no easy task . . .
Well, just finished dinner. Went back out, fired it up, gave it the smallest pedal w/ foot brake, and it stayed running in gear. Probably just need to close the secondaries back up, and leave it the heck alone! I'm not a professional carburetor tuner I may be trying to get this thing dialed in " too much"... lol. I know I had less problems when I didn't mess with it! Thanks George!