first time down the track advise?

I had a similar problem when I first put my 340 together in my dart. Had a carter HV mechanical pump on it, 3\8 line except the pick up was factory 5/16. It ran 14.1 on street tires first time out, started tuning and got sticky tires down to 13.3's. Once I got to that point I could jet up and down and it would run the same number. I put a Holley black pump and regulator, that got it in the 12.9's, everything else the same except fuel pump, it also responded to jet and timing changes.