i have a 89 f150 300. the truck sat for 2 years. installed 2 new tanks a nd fuel pump assy, fuel filter and fuel reservoir. truck run fine then started missing and now hardly runs.unplug map sensor and run desent.has 52 psi fuel pressure and 14 in vacuum. replaced map sensor with new unit runs the same.it will run about 1500 rpm and die out unplug mapsensor and runs. any ideas ?

 

I would say change the plugs but I doubt that's your problem but it would t hurt...

 

Distributor or plug wires