Hi, all I recently had my 03 z swapped to a 6spd mt and after getting an 04 manual ecu and flashing my vin to it, I had the check engine light come on. I went to autozone to use their code reader and got the infamous U1000, U1001, and also some P codes aswell, these P codes relate to both A/F sensor and O2 sensor. I talked to an educated friend and said that the U codes shouldnt be the cause of the check engine light and can still pass smog with them but the P codes are causing the light. The Mechanic that did the reflashing told me they suspect it being the ECU that is giving the problem. I am not sure as in anywhere I look no one has the P code problem just the U code. also for the swap I kept the AT harness and just wired the clutch safety switch to the IPDM.