318 Poly idling question

Alright, here's an update to what's been done.

- I did a valve adjustment, and it now runs a lot smoother (when it runs..)

- It has a new fuel pump

- New fuel filter

- I changed the gas tank last night, the old one was full of buckshot and rocks.. I put in a tank that was totally clean

- I changed the coil to a known good one

It still is doing the same thing. Idle for roughly 2 - 3 minutes, then die. It will start up again, but die quickly. No sputtering while dying, it just quits on me. Could some crap have gotten past the filter and into my line between the fuel pickup and the fuel pump? The filter looked to be good, not punctured or rotten or anything. The filter is dry once the truck dies, and only gets a little bit of fuel in it when I pump the pedal before starting it.