Diagnose this Engine problem...Please

[quick89gt]

Okay, I did think I was having problem with injectors, but now, I don't believe that is the case. My car ran fine for a few days with the 42's in it and now all the sudden it's a basket case. It will start up, run for about 15-30 seconds, then just die, as if someone turned the ignition off. there is no spitting or sputtering...it just dies. Also, if I hold the RPM's at 2,000 it will kind of miss a couple times after about 10-15 seconds, then it will just die clean...again...no spitting and sputtering. What in the hell could be causing this...if someone can figure it out, I will give you money...I'm so freaking sick of dealing with this. What's funny is that it's intermitent. It did this last week, then ran fine for 4 days or so, then now it's all messed up again. If anyone can help, I will be so thankful, this is giving me a headache. Josh