I am in a 84 f150 4x4. 4.9 Inline 6 Just started having a stumble when on the interstate. If I start to pass at 65 mph it will act like it isn't getting any gas. But if I ease into it it will do fine. Same in other gears if I try and wind out higher rpm to pass it will stumble. Recently (3 weeks) replaced fuel filter at carb and in line filter at tank. Which is a old 30 gal boat gas tank which I also just added. I've heard it might be distributor pick up or leak in gas line or clog In suction at tank or filter or pump. My last issue with the truck missing was at low rpm and turns out #6 spark plug was slammed shut. Any ideas?

 

1984 originally had computer controlled ignition and carburetor. Is it still that way?

 

Carb is mechanical. I think I fixed it. It was two loose spark plugs again!! Thanks for responding though.