Check on the Porsche website for the part numbers for starters.
http://www.porsche.com/all/media/pdf/originalparts/usa/914_USA_KATALOG.pdf
See page 74. Part 37f. I think the Y part you need is 022 133 215. Call you local Porsche dealer it may be available. The steel tube that goes into the intake bellows you may find a piece of steel tubing from McMaster Carr. that fits snug and use some glue on it so it does not leak air.