Hello, my 2003 Mustang gt began idling at over 2000rpm on my drive home from work the other night. I checked the TPS and it was working properly so i checked for vacuum leaks and found nothing. I then took the IAC off and cleaned it thoroughly and popped it back in. The car went back to normal idle after that so i thought i was golden. But after a few minutes i started it back up and it was back up at a 2000-2500rpm idle. I went to autozone and got a new IAC for it and put it on. After that the car would stall out right after starting. I feathered the gas pedal and got it to idle but now it idles between 650-800rpm. When put into gear (automatic) it will drop down to nearly 500rpm and stall out. I went back and checked over everything and found no vacuum leaks or any obvious signs that would cause this. I have fiddled with it all day and i'm out of ideas. I did fill my tank right a few hours before it started at my normal gas station, could it be bad fuel? Also there is no Check Engine Light. Any insight will be appreciated, THanks!