So my friend has a really nice and polished valve cover for the ecotec 2.0 turbo for his cobalt SS TC. I bought it off of him because I figured I could swap it out with my solstice 2.0 GXP valve cover. It's the same thing right? I changed it out and now my car idles a bit rough, engine reduced power display, and Check Engine Light!!!!!!! I removed the battery, and while I let it reset, I went ahead and removed the valve cover to check underneath, making sure nothing got under it like a rag or something. I plugged everything back in, connected battery, and tried again. This time it didn't idle rough anymore, but the CEL came on quickly and reduced engine power. I drove it around to see if it would possible go away but it hasn't. Anything I'm missing?? I just don't see why this would happen just because of a valve cover. There's gotta be something else.