some times hen i start the stang the car will die out. ill turn the key the car starts like normal, RPM's go up but then thell drop down and it will cause the thing to die. sometimes it ok. after it dies the first time i can turn the key and it will stay alive the second time around. also when i drive i get the RPMs jump around, thell flux down then up by maybe 100-300 rpm's

the car has new plugs, wires and MSD carp n rotor that i recently put on.

what could it be?

 

Sounds like a vacuum leak