Bob won't start!

Well after Bob choking and coughing on what seemed like a very large chicken bone for a very long time, we replaced plugs, and ALL fuel filters including the ones in the tank, and we came to the conclusion his FPR had gone bad, and after replacing it, the truck was running great. Honestly, I'd never heard it sound better. No missing, purring like a kitten. After a couple weeks of driving perfect, it started missing a little, and pretty rapidly declined to where it would stall and wouldn't start back up.
 
And idea why this might have happened? We think the new FPR has fouled, but any idea what might cause that to happen so soon?

If you can hook up a fuel pressure guage and get some readings. I highly doubt the FPR has fouled up on you.

Have you cleaned the EGR valve?  When you replaced the FPR, did you replace the internal fuel lines ('nut kit')?