depends on what car you are driving, whether gt or gts. also depends on if you are manual or automatic.
i looked at your profile and your model is not listed, along with whether or not its auto or manual so you'll have to be more specific
i don't know exactly, but in my manual gts in 6th gear, i think 80 mph is somewhere around 4k rpms. give or take some..someone feel free to correct me if they know the actual number.