Yeah I had the same problem, becasue I did a mini me swap on my 98 lx, and I was runing lean, and I couldn't find out why, i already changd my o2 twice, and it was still running lean. So i called honda and i told them what i did and they said becasue you put a ex head on a lx engine we cannot troubleshoot it. So i asked them if i should of used a ex ecu and he said YES. So i then i asked around at some honda forums and i was getting replys that i should use the ex ecu, well then i bought one from HAP recycling, then when i put it in it was Ideling at like 1500+ rpm, it sounded like shit, and got the same codes. And my car was still running lean, SO I said what the Fuck. Then I bought a o2 sensor form HAP recycling and BAAMMM my lean problem was GONE. So then i sold my ex ecu, and kept my lx ecu and activated my vtec with a summit rpm switch which works great til this day. . But since you have the whole engine and the ecu, you should just buy a ex engine harness. because i now that the ex has a 2 wire Idel air control plug, and the y7 engines have a 3 wire. just changing the plugs on the y7 harness won't do it, because if you have a manual for you car like a helms, or haynes, you can look at the wiring diagram in the back and you can see that the ex 2 wire go to differnt pins and the y7 3 wire go to differnt pins, so to save all that trouble and what I think will help solve all your problems is to just buy a ex wire harness.