I have a 1985 f-150 5.0 efi auto i runs great when i first run it but the longer i drive the crappier it runs it sputters until the rpms drop and it shifts down.It was really strange today i t was running good till i stoped and put gas in it and it really started to run like crap.It dont get worse or better just does the same thing every time i drive it

Have you changed the fuel filter lately?

Check your fuel pressure as well.