Are you running a tune with it?
That fixed mine a little, but I know mine has a delay if I'm in 5th and floor it. When it hits 3rd it hits hard, but it just sort of sits there for a second and seems to do nothing when first floored. It's not instant for sure.
Maybe someone else will chime in, but I think that's normal for these cars.
Sent from my iPhone using Mustang Evolution