What caused this?

For the first time last night I took my Duster to the drag strip. I was very disappointed. My first pass was in the low 18's. When I got to around 70mph it seemed like the car just didn't want to go anymore, almost like it was starving for fuel. So I just let off the gas way before I even passed the finish line. It did the same thing on my second pass. I wasn't too happy considering all the work done to the engine. Could my fuel pump be causing that problem of why it dosn't want to keep going after 70mph when the peddel is floored. It is just a stock replacement fuel pump on a rebuilt engine. Any help would be appreciated. Thanks