you might get a little less rasp with the hfc's but considering you're getting 18in. resonators it shouldn't be "unlivable" however if Chitown is hard on emission testing then get the HFC's
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2009 Carbon Fiber/Red 370z aka Trish: Sports Package, Meisterschaft full catback, Fast Intentions Longtube Headers, Injen Long Tube Intakes, UpRev Tune: Sold 
2008 Lotus Exige S Club Racer aka Bella, always leaves me smiling
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