Beyond Frustrated - Wont start/stay running

If you want to do the tail pipe test right..... hold a newer, stiff dollar bill on one half and move the other half over the tailpipe from the side, with the plane of the bill perpendicular to the pipe end and <1" away. If the exhaust sucks it back into the pipe part of the time, then that generally indicates an exhaust valve problem: burned or worn valve or seat, bad or sticking guide, open lash. Your dollar bill may get dirty LOL

The timed vacuum port can be anywhere on a carb in general. The actual pickup is up in the middle, in the throat above the throttle plates, but it can route through vertical passages in the carb to a tube down lower or up higher. Put a vacuum gauge on it at idle, or find some documentation, and you will know for sure.