I'VE GOT A 93 5.0. I JUST PUT A 255 LPH FUEL PUMP ON IT AND NOW ITS BACKFIRING THROUGH THE THROTTLE BODY. IT ALSO LOSE FUEL PRESSURE WHEN IT REVS UP. FROM 40 TO 20 OR EVEN 10.

 

Did you replace the filter too? You got a bad pump, you have a restrictive line or crap in the tank or resistance in the pump wiring. Odds are, the pump is good. If you did it right, you should have noted any crap in the tank and replaced the filter. This makes the most likely source of your issue some resistance in the pump wiring. This limits the pump's top speed and consequently, it will not be able to provide enough pressure/volume.

 

no i had a pump do that...less than 2 months old....change filter and blow through the line...then go to the pump