We were having the same discussion here:
http://www.seatcupra.net/forums/showthread.php?t=215859
If I follow everything correctly then the diagram in the link in post 29 is the "preferred" way to connect the DV and in this case "any" spring will be OK.
My DV is connected opposite to this and in the OE orientation as far as I'm aware, in which case the spring is working against the boost pressure, hence a stiffer spring is required to keep the DV shut on higher boosted cars.
If the 007 is put in OE orientation then the spring is NOT acting against the boost pressure. In OE orientation the small vac nipple points straight up.