92LT1RS

Over break I took my car to be dyno'd in Houston at HPE on their Mustang Dyno. I was happy with the 318 rwhp, but not so happy with the A/F ratio. On all 3 passes I made, the fuel mixture started out nice at 12.5, and only came up to about 12.7 at around 4000. But at about 4500 rpm it jumped up to about 13.3, and at about 5800 it jumped up again to about 13.9. If I go into Tunercat and look at the %Change to Fuel/Air Ratio vs. RPM at WOT table, I see corresponding points on the graph that mirror these. How can I bring the mixture back down and fatten it up near the top? My only concern for it is if I ever run nitrous, I don't want it leaning out on me. I guess I could just run a fatter fuel jet, but I'd rather have the tune correct first.