Nissan 350z 2007 Facelift HR 313 GT with a True Dual HKS Hi Power exhaust system with test pipes. Warm start with low revs. The exhaust sounds good on the revs, and when you put your foot down under load. But with all 350z's after market exhausts the run down has this blowing sound. This is not actually the exhaust blowing at all, it's caused by the flexible part of the pipes by the cats, they expand when you give some revs and retract when pressure dies down. After putting any after market exhaust system on your 350z you will start to hear that sound and the louder the exhaust you pick the more you will hear it.