6.0 Falls Dead, Cranks Up?????????

[JJAB]

Ok fellows, you have helped me throughout this swap. I have completed the swap and the tuner has come and completed the in person custom tune. It has since been two weeks since the tune. Four days ago, the blazer would crank and run for thirty seconds or so and die out; would only stay running with your foot on the gas pedal. Long story short, I had to re-vent the gas tank. Prior to reventing the gas tank, I had vented the tank by the vent tube or hose that goes to the charcoal canister. I guess it wasn't sufficient. Nowm while driving the blazer, when I come to a stop, sudden or not, the blazer falls dead, but will crank right back up. Thing is, this was not a problem when the tuner was in the vehicle. Help me out if you can.

Here's a little more information:

Single gas tank with EP381 fuel pump, ECM is pulling no codes, fuel pressure regulator is new,truck intake, all sensors are new.

I am running a very short, straight air elbow with a rather cheap, short a filter. I just haven't upgraded it. Couold this be my problem?