What caused this?

The fuel filter looks fine, the last time I checked (which was about a month ago) the linkage goes all the way back when the peddle is to the floor. The engine has well over 1,000 miles since it was rebuilt. The major mods include:

-All new pistons, and brought to "0" deck clearence
-340 cam, lifters, and valve springs
-Block is bored .30 over
-Original 318 heads had 3 angle valve job, port-polish
-Edelbrock 500cfm 4-barrel, and performer intake
-ECU orange box

I still think I need to beef up the fuel pump and get rid of the stock replacement unit thats on it now. I have gotten on it a few times on the street and seems fine. It never acts like its starving for fuel, but then again I have never had the car floored from a dead stop going up to 70mph. The car ran fine at the stip until it hit around 70mph and thats when it started bogging and acted like it didn't want to keep on going.

When the engine was getting rebuilt the fuel line was replaced from gas tank to the carb. Just about everything else has been replaced as well.