After I let my civic run for a bit, it will lose power and die, i will try to start it again but it won't stay running, i will have the pedel to the floor and it would bearly run. I got a d15 ecu thats not for the vtec i don't know if that would be a problem, but what is wrong with it.

 

Any check engine light?

If not, try replacing cat converter. Sometimes if it is clogged your car will start up and run for a bit then gradually die off.