In my experience with muffler places(we have 200/300tdi engine swaps regularly in rover defenders) they are lazy and use whatever is around/available. The factory down-pipes are 2 3/8" for a reason, forced induction motors need to be able to flow the spent gases out readily. But they use crush bent 2" pipe which really restricts the flow and power. My butt Dyno can feel it from open down pipe to full pea shooter exhaust.

If you don't specify what you want(2.5" crush bent I think would suffice in this instance) then you never know what you will get with these type of places. Factory benz pipes are not crush bent for a reason...