Wont run

87 F150 with 302 EFI single coil ignition system.. reliable vehicle turn it off a
few hours later went to it and crank but no start I am a mechanic with 10 years
experience and IV got up with a well-respected veteran mechanic over this
issue we are stumped.   I replace the ignition coil and the distributor since we
have got it to crank very hard to get it to crank and bucks and it jumps and
backfires like mad out the pipe it did idle for a second or two once or twice but
will not stay running. Would only start after turning over a lot and opening
throttle all the way backfires and runs really aggressive at idle and throttling
thought catalytic converter what's plug took off exhaust system at the headers
same issue.. double check the distributor timing is perfect map air sensor is
good coil new distributor new plugs good ignition module good good battery
Good Grounds where ground should be good relays good fuses..   never had
this issue truck ran smooth before I turned it off then tried to restart and had
this issue I didn't bump pool on or touch any wires besides replacing coil
distributor and plugs and troubleshooting coil voltage and spark plug Spark..
weak spark at the plugs but this vehicle has always had this problem.  I have
good gas pressure at the rail good gas filter and air cleaner.  Has any one seen
or had this problem or hear of it and could point me in the right direction?