DV is easiest / safest place to take a T from, if for some reason the split you put in the map sensor line starts leaking or comes apart when your going flat out the ecu will think the engine is consuming less air than it actually is, so will put less fuel in, see where this is going? This is also true of the fuel pressure regulator, the fuel pressure could drop suddenly.

If DV line leaks then the DV will open and the boost will drop