When redoing the muffler system, used the disc inserts from Car Chemistry. These are available with 1 to 3 discs, and center tube plugs for either a partial restriction or a plug that forces all the exhaust gases into the discs. These plugs do not have to be used.
Did not measure the db, but the system is quieter. Used the three disc system without the plugs
Available from Summit Racing.
It has been mentioned that the discs, with or without the plugs , create too much back pressure , but for street driving have not had any adverse effects.
www.carchemistry.com