I called HMF directly for this same question. They told me that as far as the sound the utility pipe is at about 114 decimals (I think maybe higher)and with the quite core it brings it down to about 94 deciamals which is almost factory. The only thing bad about the quite core is that it will take some power off of the pipe but i went ahead and bought the utility with the quite core and jet kit with the K&N filter. The # to HMF is 216-631-6980 ask for mike or dan they were real help full to me. But don't buy the pipe from them you can get it a lot cheaper from www.worldwideperformanc1.com I hope this helps ya.