The Cobra resonated is the one to go for, on Friday we fitted the very same to a HR and it sounded great, this too had the usual break between the mid and rear.
The Y pipe is optional, you can just replace the mid ad rear.
More info can be seen here - http://www.350z-uk.com/topic/63096-cobra-sports-exhaust-from-cougar-store/
Drop us a call or PM and we'll be happy to help...