91' Ford F150 straight 6 manual

So we just traded a Crown Vic for this
truck. The day we got the truck it broke
down and everyday since then (about
2 weeks) breaks down 2 to 5 times a
day! What happens is in the morning it
starts fine then after about 15 mins of
driving it starts to get a sputtering
sound. Followed by bucking and
begins to sound like its trying to
cough. Step on gas and sputters till ot
dies. After that it wont start. Battery
hardly has enough juice to turn over.
Have to get a jump and maybe it will
start. We have put in a new battery
have had the alternator checked  and
the module. All is in working order.
Have done the EGR thing.
Disconnected the vacuum hose from it
and it made truck over heat and run
worse. Cadiletic converter drilled and
cleaned. No emissions where I live so
dont matter. Also replaced the module
on bottom of rotor. Plugs and wires
look good. Still same problem. Im not
a mechanical guru but am also not
mechanically stupid. I have worked on
cars my whole life. I just need to start
with the cheapest fixes first cause of
my budget. Please help