Ok My 1990 Mustang gt just shut off while i was driving i tryed to crank it and it wouldnt crank.?

so i got my friend to tow it home. i left it about 5 or 6 hours sittin and i came home it cranked right up and killed about another 2 minutes or less later. the fuel pump still primes when i halfway turn the key but it just will not start i have a in tank fuel pump and also about 1 or 2 feet after the fuel lines run there is another round cylinder looking thing. what is that round cylinder thing? is it my fuel filter? it looks old and want to no what it is and why my car wont start idk if this year was made with an intank fuel pump or if it was an out of tank pump. there is alot of performance stuff added on to it also including the fuel lines that i see running to the pistons, they are all aluminum or steel and have a pressure gauge under the hood which sits at aqround 40 psi so i no it cant be stock. why wont my car start and what is that old cylinder thing i see out of the tank but by it?