Sorry to hear about the light issue. My car done the exact same thing. 20 miles away light came on for the rest of the trip. So what are JT planning on doing for it? I think I will go with the fidanza as well. As far as idleing goes I too have a little rise and fall in rpms. Spoke to them about it they want to wait on exhaust to be completed before making any tune changes. Be the way what exhaust you have ordered???