Wont stay running
 

My truck turns over and starts but only for a couple of seconds, it makes a popping noise when it is running and their is a gap between the exhaust manifold and Y pipe, could that be the cause? it has all new spark plugs I cant take it to autozone to read the code so any ideas?

It is an instant stall i think it may be a bad ground i put new heads on that are painted black, i also need a PVC rubbing fitting because im using tape to hold the hose into the valve, the fuel pump is woking.