I am having trouble with my 2001 mustang. The first thing it is doing is when I start it, it the rpms keep raising and lowering and the car revs up then stops. After that when I put it in drive it either dies or almost dies unless I push on the gas quick. Last but not least I am getting horrible mpg. I have swapped out the tps, neutral safety switch, and spark plug, I have also cleaned the throttle and IAC a little. Any help would be greatly appreciated. Thanks!