Ok this is a weird one, I think I know what it is, but lets see
Alrighty, so I am going to go see my gf the other night up at her school, I am about to pull into a gas staion to get my lotto tickets, but I see a Ferrari 348, thought was a 360 till my bro pointed something out, so I race him, dont get spanked to badly either, his tail lights never left my nose. (cus we ran out of room but ill take what I can get). Anyways so after he turns off I stop at the next gas station, I come back out turn the car back on and boom check engine light, yes I allowed a cool down, and the gas station was like 5 mins after the race, but yeah check engine light. So i turn the car off cus I just changed the oil last week and wanted to make sure it wasnt leaking or anything, second dot, all good. So right then I figure the warmer weather now is setting of the rear O2 sensor as I have a straight thru turbo back with mechanical fix, an O2 spacer. So I drive up to see her its on the whole 1.5 hours. Next morning its cooler, cold actually, turn on car, no l light. Drive to work, no light. After work turn on car, light! This morning light! So is my guess correct, is the warmer weather producing less dense air causing the car to run richer making the sensor pick up on the subtraction of the 2 rear cats, even with the spacer???