is it one peice?? if so it may be standard. i cant see anyone removing subframe to fit new one. i bought one with 109k and it was factory exhaust so chances are you have factory too. theres different grades of stainless and to cut cost i think some are not as pure stainless as they should be. they start of rusting in spots and over a few years they are covered but doesnt corrode through like normal steel. just because its rusty dont think it didnt start out as a stainless.