I had a similar thing happen.....my first time to the track in my newly built challenger (eddy headed 440), I made a pass....13.80 (I forget the mph, maybe 103?). Man I was po'd....

I go back to pits to figure out what's wrong...I know it should have ran better. I find that when I put the carpet in....that limited how far the throttle pedal would push down (I only had primarys opening on my 800 DP). I adjust the cable and the next pass was 11.70's at 116 mph.