Hello everyone, I am a newish kia owner and bought the 2002 Kia Rio. A bit of background before the issue. I changed the engine (1.5L) for the 03 1.6L and it worked fine on the day I took it for a test drive. The next day it was acting really rough, loss of power and the check engine light came on. It will buck and choke on gas then act normal after 30 seconds. So now day 2 I go to start it and it wont even idle without reving it, and the "choking" became worse, so I changed the ECU for the 2003 one and now the fuel pump wont prime. So I changed back to the 2002 ECU which I had in it before when it was running... and changed the fuel pump for one I knew worked and still the same issue no priming. So does anyone know what could be going on here? Bad ground? Both ECU's fried? I am at a loss. I did check the fuel pump fueses and relay.