I have a 1990 f150 with the 5.0 efi it started out with a stumble or two going down the road like it would die real fast and start running again now it starts up runs for a few seconds and dies I put a new o2 sensor in and also a brand new full duel exhaust with headers check engine light comes hardly ever I know that don't meen anything though and help would be great as this is my work truck thank you all in advance it also has a new fuel pump tank and lines was just put on 6 to 8 months ago front tank is blocked off due to having a hole in it

 

If the truck dies after the engine is warm or hot, it could be the TFI. That's Thin Film Ignition that is on the distributor. If it gets hot, it breaks contact but will reset when the engine cools some. It will eventually not start at all. If you are handy with tools, this is a DIY project. Parts are at Rockauto.

 

Here's a few acronyms for you to look up that may be related ; TFI, ECT, PIP and also the coil can act up.
You should check the computer for stored codes (it knows more than you do about what's wrong) and you can also check your fuel pressure (with a gauge) - should be 30 to 45 psi, preferably over 40.
Couple things to check into anyway.