This part does have a very significant undercut: the fitting edge. You will definitely need a two part mold for this. And if I see it right in the second picture, even the two part mold have to make use of a bit of flex of the final part, as the upper face seems to be curved inwards.

place the part as in the second picture. seen from above, your part looks a bit like an egg, your mold split should be a vertical plane through the tip of the egg, and the opposing corner. It seems like this is exacly the split, the original manufacturer made, as I think I see a seam there.

Please suggest the best approach to fabricate this motorcycle exhaust tip of carbon fiber.  I can use this part as the plug if necessary.  Piece is 3-1/2"x4-1/2"x5-1/2".  Except for the hole (which can be plugged and drilled out later in the final piece, it doesn't have any undercuts, so I'm hoping it may be possible to make a one piece.  Or split mould best?  Female mould best, I think, because of the large end dimension which fits into the metal can of the exhaust is the critical  part. (you can see that edge as the rougher finish 1/2" flange on the large end of the part.  Here are some photos: