1st ,you could get it pass if you can ask the Tech to put a fan in front of the car blow the cold air to the radiator while doing a test. Or you can test the car on the colder day 2nd, you could retard the timing little bit. This is a 20/20, by retarding the timing car will run rich therefore HC and CO will increase. Plus our car is computer controll timing I'm not sure this helps much. 3rd Run higher octane or decabornized the combustion chamber. I don't know why you said after installed EGR delete kit it got better, It should the other way around. The EGR system main function is to reduce NOx.