rough idle for 30 seconds after starting

I am trying to figure out whats up with the stang. 93 5.0 LX. After sitting all night and starting up the car it starts but if you dont press the gas it starts dying out. If I keep the gas pressed for about 15 seconds or so it stays running and runs fine. I checked the vacuum system and the only thing I see there is down at the front of the passenger side there is a black box with hoses going to it. It sounds like there may be a leak there. The timing is at 14 degrees, new plugs, dist, wires... It has been doing it for a while. Any suggestions?

Thanks...

Try cleaning out your Idle Air control with carb cleaner. IAC is the cylinder located on the side of the throttle body.

Try cleaning out your Idle Air control with carb cleaner. IAC is the cylinder located on the side of the throttle body.

Yep, clean the IAC and MAF, and if it still hesitates/stumbles replace your O2 sensors.

Is the car stock or is there work done to it?

Make sure the IAC is clean and operating properly, check to ensure that the TPS voltage is at the proper setting and the idle speed is also set nicely.

Thanks guys. I will check and clean the IAC and the TPS tonight. I have few mods on the car, FlowMaster cat-backs, K&N filter charger... Thats it.