xxvegask1dxx

hello im new to all of this but i have a issue that i would like to try to resolve.
I have an 86 mustang lx 5.0 / it has 147k miles on it. i live in las vegas and the car runs hot. but when the car gets to 200 degrees it wont go any where past 3k rpms when im driving but will if its in neutral. i dont understand why. when im driving and stop driving theres a really bad gas smell coming from the car and im not for sure if it has anything to do with it. the car gets to 220 on the freeway and i know that not good. Also when the car get warm the idle will jump from 700 rmps to 1200 rpms over and over and it will slowly stop.
i have no damn idea what it is.. please help