98mustangkidd

So the past two weeks I've been starting my car and the first start it cranks over for awhile then finally it will start up, but sounds like its about to die for a second then it goes to a good idle. When i go somewhere like say 711 and i walk in and walk back out ill try to start it and it will start right up with no problem. It seems like its not getting enough fuel or something then finally does. But then i have another problem... I use to have a hanging rpm problem but that went away with a new iac valve. The other day (i know this is bad) but i was at school and a kid was standing there and he was like let me hear that mustang and i revved it up till i got to about 4000 rpm... then all of a sudden my rpm's started to hang. I drove to go drop my girlfriend off at her house and change for work and i shut the car off. Came back out and i started it up and it wasn't hanging anymore. Does anyone else have this problem? Anyone that can point me in the right direction of where to go? thanks