help!!!!....running problem

Ok i need alot of help here this has totally got me and my friends stumped. Ok we just put a motor in my car, i had the motor bored .030, explorer upper and lower, e cam, and gt40p headers. ok we put the motor together and correctly i might add ( i have alot of faith in justin ). well got it in the car and try to start it it runs then shuts off. ok so i replaced the fuel pump and filter, now it still wont start...injectors not working... so i replaced those. now the fuel problem is over...but now when you start it it will try to idle and its missing pretty badly and it pops through the intake and the exaust... we checked..double checked and triple checked the timing everything is right. we have checked the map sensor, mass air, IAC, distributor, TFI module, everything electronic except the computer. before we put the motor in the car had been sitting for 6months and the battery has been dead. thought maybe the computer was in default but i highly doubt it. it acts the same way even if you pull the spout connector out so i would think that that eliminates the computer. but if you rev it above 2500 it clears up and runs just fine. im lost can anyone help me here....please!!..

i was reading about the KOEO test. ive done that before, but it says you have to get the car to operating tempateure. we cant even get it to run that long.

ive also been around a cammed car alot for the past 3yrs bc all of my friends own modified mustangs. but we have gotten together on this problem again and we might think it is a vaccum leak it must be an awful big vaccum leak to cause it to run that bad. any suggestions on where it could be coming from? the hose going from to the intake to the vaccum cluster on the firewall is hooked up. any other hoses or leaks anybody can think of??

well i think we found the problem...the cam might be out of time itself. we are guessing and hoping that it might be off a tooth or two bc that would not be noticeable unless you took the front end apart and looked. hopefully this will be it..hopefully. i just dont know what else would cause it to pop through the intake and exaust.