If its randomly doing it and not under one set of circumstances I would check basic things first like plugs, coil packs and filters. is there any codes on the car now still and does it stall just sat still on the driveway? could always change the crank position sensor, relatively cheap and easy to do and would eliminate one possibility. if its still hunting for an idle and going up and down then yeah the throttle body would be worth a go at and then I would check the cam position sensor, timing related rather than air leaks unlike the original code but depending on the age and history of any timing jobs being or not being done depending on if its belt or chain then it may be the timing out slightly if its randomly stalls. If its a turbocharged engine an air leak would normally be noticeable all the time, have loss of power, constantly hunting for a stable idle and under load too and would have to be a pretty big leak to stall and you can usually hear a different sound through the turbo when the pressure is built up and then let off the gas kind of like a blow of valve noise on the modified diesels the kids fart around with. hope some of this helps and you get it sorted.