Question on my ECU

On my last question I stated how 4 difffernt fault codes came up. I was told that I should try a new ECU. Also I replace the wire harness but insted of the NT for my 2.0 engine I use a T wire harness. My question is: can my ECU control my engine through the new harness or is there a different ECU I should get for the T wire harness? Also is there anyway or anywhere I can test my ECU? or a place I can go to get a new one and test it before I purchase it? All information is greatly appriecated.