this is definitely 2.5" then.i couldnt find a definite answer on the size of the MAM.
in fact, i feel like they might have offered both 2.5 and 3.
is there any rust near the flex sections, or anywhere other than the hangers for that matter?
There isn't any significant rust I'd be concerned about, but you'd probably have to torch the bolt in the o2 bung if you wanted to remove it. The midpipe was probably installed for about 20k miles, and I keep my car garaged.