As said its sold, But I'd never seen a Gen1 with the Bottle Neck where it joins the B-pipe before, that was only on the Gen2's unless it was on the very late gen1's anyway its irrelevant now!
My Gen1 N1 Is a straight 2.5 right to the flange, 100% as it came from spoon as far as I know, All the welds are original so hasn't been modded, Bottleneck May have been an addition to later Gen1's or something