My old 87 F150 4.9L sputters and stalls after engine braking (downhill, offroad) has ocurred. Once restarted, have to rev up to 4000 rpm a few times, get the odd backfire, then its fine again for a while. Also have similar hesitation after ~15 highway driving. Timing was adjusted a while back, could that be it? Have replaced fuel filter and run some fuel injector cleaner recently.

 

i think u should check ur timing and make sure its 10 degreas btdc

id also do full tune up plugs wire cap rotor
air filter pcv valve crank case breather
check the throttle body "clean if nessisary"

 

Correction and update, timing was adjusted after the timing gears were replaced. Can the gears be installed 180 deg out, i read this is one of few engines that can still run, albeit rough with that issue? Also, found the oxygen sensor (front ) wires fried off, how much can that affect the ignition?