This! It takes 3 things to run the engine. Air, Fuel and Spark. By modifying one of th e3, you could easily be changing the way the vehicle runs. Too much air can change things very quickly.
Have you reset the paprmeters? Every time you get gasoline they should be reste. They are nothin gmore than an average. The only proper way to tell is keep a log of How many miles you drove with how many gallons you put in.
What other mods are done to te car? Any suspenison work? First things that come to mind are Pinion Angle and unbolt the driveshaft from the Pinion Flange and rotate 180 degrees
Welcome. Also form Florida. Not sure if you are on FB. We have a huge community here in South Florida called Stangs of South Florida. Very active group
The sportline suggests 1.6" front and 2" rear drop. The pro Kit suggests 1.4 and 1.5 rear. Depending on valving the ride with the sportline might be too harsh