It makes no difference. Any difference in acceleration is in your head.
Your transmission is a 4 speed, the 4th gear is overdrive (less than a 1:1 ratio). Turning it off simply prevents it from shifting into 4th.
"I'm not driving too fast...just flying too low"
-03 SB Cobra vert- 2552 of 5082 Born 02/25/03
90 7up vert - new project-07 DSG Focus -DD