So I have 2008 Mustang Gt premium with a 4.6l v8 sohc, I took it for a spin and on a long empty stretch of road, i decided to go fast cuz who wouldn't tbh unless im alone on this but as soon as i hit xxx mph it stopped going any further even tho i had the pedal to the floor, i double checked the VIN and it is an original gt with the 4.6l b8 sohc but I've read that it should be xxx mph top speed? Anything advice to help out?