just got a remus back box for my vr syncro so hears the question i had to cut back box off as its one piece with the twin silences went to fit back box but the diameter is exacatly the same size so the question is do i need to hit the back box onto the pipe until the flange opens up on the back box to fit the existing exhaust pipe sorry if it sounds dumb but it cost me alot of money and i dont want to start hitting it if i dont have to hope what i have described makes sense