You need this or the choke won't work correctly, unless you improve things (a lot) by installing a new
Electric choke kit.
Necessary if you're keeping the EGR system operational.
Plowing through the engine bay yanking and cutting and disabling stuff because "That's a pollution control, so I'ma git rid of it!" is a thoughtless and unreasonable thing to do. See
here for info on what the various systems are and which ones are worth keeping vs. removing.
That's the OSAC valve, notorious for causing mushy driveability/hesitation. Bypass it (hose directly from the correct port on the carburetor to the distributor).
It did originally -- perhaps someone dropped in a (much) later "Lean Burn" distributor. You definitely need vacuum advance for good driveability, performance, and fuel economy, so either swap the '73 distributor into the '74 engine, or get a new distributor from Old Car Parts Northwest as described in the
HEI upgrade article.