Trucks been mesed up for long time

OK so I bought a 1993 ford explore with a v6 4.0, when I got it we found out one problem was the fuel pump had a huge hole in the feeding tube. Fixed that but it was still not getting over 3 rpms and stalling out, and jumping to higher rpms and jumping back down all at the same time my foot was to the floor and I was steady losing speed. So then I replaced the mas Flo, idle air motor, and the other one there that regulates the throttle. Also I change the fuel filter and it has half a tune up but still problems. Till I got a code reader ran on it then all my problem magically disapered till now there back and I have no clue what is wrong. I am also getting a strange gurgling from the fuel tank when my fuel pump turns on? I need help. Oh code reader only said it was getting improper throttle response but no reason why.