I think Flowmaster has discontinued that system. I know Gibson and Walker discontinued their systems for our motorhomes. That is one reason I went with Banks plus their extensive testing and development. Theirs is all stainless steel with the exception of the tail pipe which is aluminized steel so no rust problems. You can't get a better system if you can stand the price.
Roy & Sabine Lyons
98 Itasca 35' Class A Gas with Banks Powerpack
98 Honda CRV Toad