2004 Mustang Gt Conv- loose power in 5th gear want more pull

[Lawdog]

U7146
2004, Mustang Gt Conv
would like some custom tunes

[MesaRec]

Sounds like you need low end torque, and the tuner will not be able to produce a dramatic effect except in throttle response.
That said, you should get rear end gears. 3.73's or 4.10's.