For those that have chosen to keep the stock b-pipe and muffler, but have modified your y-pipe and cats, what is the tone of the exhaust like at higher RPM? With the addition of only r/t cats, I noticed a much louder "solid" tone with no rasp around 3,500 RPM which has become quite pleasant, coupled with a noticable performance increase, but the tone of my exhaust around 6,000 RPM has dramatically changed. The sound is very raspy and almost sounds quiet for some reason. Would the addition of an aftermarket y-pipe give the car that clean, "open mouth" sound that I am looking for, or would only an aftermarket muffler provide the tone I have described? BTW - The car is a 2003 SB 350Z track with just a K&N drop in filter and R/T cats. Thanks for any helpful comments.