No Check Engine light. I didn't even go through with getting them coated or wrapped either, I just couldn't wait. I live in sunny Fort Lauderdale where its Summer already. It was in the mid 80's today, so I guess keeping the O2 sensor hot is not really a problem down here. Oh yeah, I know how bad it is to race on the streets but I had to see what the RS is capable of now. I ran against a '97 Eclipse GS with headwork, cams, intake, sprockets, and high compression pistons, thats what he said. Stock Exhaust. We got a red and I did my thing, he rolled a full car length in front of me before the light even changed, but I laughed when his wheels spun and I jumped across the intersection. He was in my rearview all the way. I took third to red and dropped off after. I was amazed at the acceleration the RS acheived. Its not just a good looking car anymore.