yup, thats the fuel pres test port,, the regulator is the round gold thing,, and apparently it has been replaced sometime in the past,, unless you see an allen head screw down in that hole.

so,,, you know whats coming to mind now.................
something that seems to always be the problem when everything else seems right??

Ignition switch.,,,,

its not easy to install if your a tad lean on wrenching so get a trusted friend to change it out.

its really worth shot gunning a part this cheap to see "if" it fixes the issue.

something is over heading within your 11mile trip to work... again i am speculating something is over heating based on what you said.............

oh,, heck,, by the way.........

do you have a smog pump down on the lower left of your motor.?

remove belt, grab the smog pump pully and spin it,, if its binding up,, that could be adding some load on the engine,, so that when you are driving along and you happen to let off the gas coasting down hill or something, the extra load will litterally slow down the rpm enough to shut off the car.

this "feel" test i mention is only best done when the engine is hot unfortunatly.

once upon a time i threw a belt a couple times because of the smog pump pully locking up.

you can short belt the engine by removing the smog pump,, and the plastic impellar on the face,, then route a shorter belt on, the belt will barely clear the metal case of the smog and you can just leave the smog pump on the car.