Just some comments on stainless steel. There is no such thing as a 'cheap grade" of stainless steel. There is Austenetic ( 304, 304L, 303, 316, 316L, etc), Ferritic ( 409 ), Martinsetic ( 440 A,B,C, 416 etc), Precipitation Hardening ( special numbering system). All have their applications. Ferritic and Martensetic are magnetic. Austenetic stainless steel becomes slightly magnetic as it is workhardened. 312 fillermetal ( Austenetic) is magnetic because it has ferrite formers in it. 304L, the darling of the exhausts does not like sulfuric acid and will corrode at the welded joint if has been overheated while welding. Welding 304L with carbon steel filler metal is a good way to destroy the whole intent of the stainless steel exhaust system. I have seen this done by shops that want to save money. Not your money! In a damp climate where the liberal use of salt on the roads in the winter is a problem, 304L stainless is a good choice, if it is installed correctly. I am satisfied with the aluminized steel for my application. GregH